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Tennis Court Surfaces and Court Speeds

What Court Surfaces and Tennis Balls Do Grand Slams and ATP Tournaments Use? What Speed Are They?

Earlier this week the US Open announced that they were changing the brand of court surface used at the tournament for the first time in more than 40 years.

The switch sees Flushing Meadows use Laykold hard courts made by Advanced Polymer Technology, replacing the DecoTurf that had been in use since 1978.

This change in New York follows on from Melbourne's change earlier in the year. The Australian Open moved surface supplier to GreenSet Worldwide for 2020 away from California Sports, who they had used since 2008.

We've also seen several ball changes in recent years with Dunlop striking a massive deal to supply the Australian Open Ball and Wilson replacing Babolat as the French Open Ball.

With that in mind, what other court surfaces and tennis balls are currently in use on the ATP tour? Are we moving even further towards surface homogenisation and just one or two suppliers dominating? Let's take a look.

Grand Slam Court Surfaces, Court Speed and Tennis Balls

Aus Open Dunlop Balls
Tournament Supplier Surface ITF Court Pace Rating Ball Used
Australian Open Greenset Worldwide Australian Open GreenSet Category 4 – Medium-Fast Dunlop Australian Open
French Open Supersol Red Clay Category 1 – Slow Wilson French Open
Wimbledon Mother Nature 100% Perennial Ryegrass N/A Slazenger Wimbledon
US Open Advanced Polymer Technology Laykold Cushion Plus System Category 2 – Medium-Slow Wilson US Open

ATP Masters 1000 Court Surfaces, Court Speed and Tennis Balls

Masters 1000 Balls
Tournament Supplier Surface ITF Court Pace Rating Ball Used
Indian Wells California Sports Surfaces Plexipave IW Category 2 – Medium-Slow HEAD Penn
Miami Masters Advanced Polymer Technology Laykold Cushion Plus Category 2 – Medium-Slow HEAD Penn
Monte Carlo Terre Davis S.a.s. Red Clay Category 1 – Slow Dunlop Fort Clay Court
Madrid Open Celabasa Sport Red Clay Category 1 – Slow Dunlop Fort Clay Court
Rome Masters Terre Davis S.a.s. Red Clay Category 1 – Slow Dunlop Fort Clay Court
Rogers Cup California Sports Surfaces DecoTurf II Category 3 – Medium HEAD Penn
Cincinnati Masters California Sports Surfaces DecoTurf II Category 3 – Medium HEAD Penn
Shanghai Masters California Sports Surfaces DecoTurf II Category 3 – Medium Dunlop
Paris Masters Greenset Worldwide Greenset Grand Prix Category 3 – Medium HEAD Penn
ATP Finals Greenset Worldwide Greenset Grand Prix Category 3 – Medium Dunlop

ATP 500 Court Surfaces, Court Speed and Tennis Balls

Tournament Supplier Surface ITF Court Pace Rating Ball Used
Rotterdam Greenset Worldwide Greenset Grand Prix Category 3 – Medium Technifibre X One
Rio Open   Clay Category 1 – Slow HEAD Penn
Dubai California Sports Surfaces DecoTurf II  Category 3 – Medium Dunlop Australian Open
Acapulco California Sports Surfaces Plexipave Category 1 – Slow Wilson US Open
Barcelona Celabasa Sport Clay Category 1 – Slow Dunlop Fort Clay Court
Halle Mother Nature Grass Unknown Slazenger Wimbledon
Queens Mother Nature Grass Unknown Slazenger Wimbledon
Hamburg   Clay Category 1 – Slow Tretorn
Washington California Sports Surfaces DecoColor Category 4: Medium-fast HEAD Penn
Beijing California Sports Surfaces DecoTurf Category 3 – Medium HEAD Penn
Tokyo California Sports Surfaces DecoTurf Category 3 – Medium Dunlop
Basel Greenset Worldwide Greenset Grand Prix Category 3 – Medium Dunlop
Vienna California Sports Surfaces Rebound Ace Synpave Category 2 – Medium-Slow Dunlop

What Other Types of Court Surfaces are Used Across the World?

Carpet Court

Tennis is probably one of the few games in the world that is played on a variety of surfaces be it grass, clay or hard courts each of those surfaces has smaller subsets made up from different materials like concrete, artificial grass and acrylic.

All court surfaces go through a rigorous testing procedure before they can be approved as an official surface by the ITF, the tests take into consideration friction, energy restitution, topography and consistency.

The types of Tennis Court officially in use across the world are:

  • Acrylic / Polyurethane
  • Artificial Clay
  • Artificial Grass
  • Asphalt
  • Carpet
  • Clay
  • Hybrid Clay
  • Concrete
  • Grass
  • Other, e.g. tiles, wood, canvas and modular systems.

How is the Speed of a Tennis Court Surface Measured?

A Sestée in Action

The ITF measure the speed of a surface using a system called Court Pace Rating or CPR for short. Any court that is used for a tournament has it's own unique Court Pace Rating.

The Court Pace Rating System measures the effect the surface has on the tennis ball which again takes into account friction, which looks at how much the balls velocity changes after it has hit the surface and also vertical restitution which factors in the time between successive bounces.

The CPR test needs various apparatus to be carried out including something to fire out a tennis ball at a set speed such as an air cannon and then a piece of equipment known as a Sestée, pictured above.

I won't go into the complexities of how it works, but basically, the Sestée uses laser technology in its two boxes that can reconstruct the trajectory of the ball and calculate pace. The ball is released from the cannon at 30m/s and at a 16° angle with no spin being imparted on it.

The Sestée can measure the following:

  • Vix = horizontal inbound velocity (m/s)
  • Viy = vertical inbound velocity (m/s)
  • Vfx = horizontal outbound velocity (m/s)
  • Vfy = vertical outbound velocity (m/s)
  • e = coefficient of restitution (COR)
  • μ = coefficient of friction (COF)
  • T = mean ball temperature for test location/sample (°C)
  • c = temperature coefficient (0.003)
  • eT= adjusted COR for temperature T
  • a = pace perception constant (150)
  • b = mean coefficient of restitution for all surface types (0.81)
  • CPR = Court Pace Rating

where:

CPR Equation

Once the pace of the courts has been measured, they are placed into categories:

Category Court Pace Rating
Category 1: Slow ≤ 29
Category 2: Medium-slow 30-34
Category 3: Medium 35-39
Category 4: Medium-fast 40-44
Category 5: Fast ≥ 45

What is Court Pace Index?

court-pace-index-wtf-historical

Court Pace Index is a completely independent method of measuring court speed and comes directly from Hawkeye.

Using their triangulation camera system, they can calculate the speed from in tournament play.

CPI shows the actual speed of the courts as it's measured during real matches on the main show courts throughout the tournament to produce an average over seven days.

CPI is calculated from the following:

CPI=100(1-μ)+150(0.81-e)

  • Where μ is the coefficient of friction
  • e is the coefficient of restitution

Again please remember here CPR = an ITF speed rating given to surfaces in a lab. CPI = court speed calculated from Hawkeye data from the main show courts during a tournament.

Examples of Court Pace Index

Speeds in 2016

Court Page Average

Speeds in 2017

The Australian Open is not listed here, but it was rated at 40.

court-pace-index-2017

Additional Reading

How to Solve the Court Speed Problem

court-pace-index-hawkeye

Most players and fans are acutely aware that the surfaces have slowed down over the years. This done for a variety of reasons but the main one is to do with the length of matches and TV money. 

The video below from 2013 talks about this at the fifty-second mark:

My opinion is that there needs to be more variety, so players have to adapt. One solution would be that an outside body predetermines the speed of the court at any given tournament and it can't change year on year or at the discretion of the tournament organisers.

So as an example, the US Open has to play at a set speed every year, and it can't drop below or exceed an agreed threshold.

There'd be no more putting more sand into the Laykold mixture to make the surface rougher; it'd be made the same each year for all of the courts at Flushing Meadows. And it'd be a fast hard court, as it should be.

By using that approach, you'd be able to have a wide variety of court speeds on tour. With the right rules in place and planning, it'd be possible to have courts ranging from one end of the spectrum to the other throughout the year.

This allows players to be tested on a variety of surfaces of which some play super quick, some play in-between, some bounce high, some bounce low and some play slowly. The key is variety, and I think you will only get that with some kind of regulation in place.

Frequently Asked Questions

Clay Supplies

Some common question I've received after writing several posts about court speed and surfaces over the years.

What is the ITF Court Pace Rating?

Court Pace Rating

The ITF classifies surfaces into one of five categories according to its Court Pace Rating: 1 – Slow, 2 – Medium-slow, 3 – Medium, 4 – Medium-fast, 5 – Fast.

This is not a measure of the speed of the court at the tournament it is used; it is purely the speed of the surface when it goes through classification. 

For example, if I create a surface called peRFect Speed Plus and I want to be classified by the ITF, I'll submit details of the surface and supply a sample of it to be tested to receive its court pace rating.

A surface type can have multiple classifications to provide a more extensive offering for buyers. Laykold, for example, has the Cushion Plus surface available in Category 2, Category 3 and Category 4.

You can see an example of a surface classification certificate here.

How Do Tournaments Determine Court Speed?

Laykold Speed

Tournaments will first seek a court supplier to lay the courts for their tournament. For example, the US Open has chosen a company called Advanced Polymer Technology for 2020.

The choice is usually determined by the surfaces the supplier produces or has access to. In the case of the US Open, Laykold is the surface of choice.

From there it's a case of the tournament and the supplier liaising to produce a surface that plays at the speed a tournament wants.

A good example here is Miami, which like the US Open is played on the Laykold Cushion Plus System. They wanted a surface that had a similar speed to other ITF 3 Medium Pace-Rating tournaments.

The supplier then customises its product mixture and installation to tweak the ball speed to get the desired result. This is done by changing the underlying layers of court and the topcoat, which has sand particles in which impact ball speed.

The key takeaway here is that surfaces can be altered significantly in speed and they do not just come as an out of the box solution that plays according to their ITF rating.

Are All Clay Courts The Same?

Clay Bricks

All clay courts at tour-level are mostly the same as they're produced from red brick dust. However the way they're laid, the substrate and the underlying surface can differ.

For example, the French Open has the following composition:

  • Redbrick dust: 1 – 2 mm
  • Crushed white limestone: 6 – 7 cm
  • Clinker (coal residue): 7 – 8 cm
  • Crushed gravel: at least 30 cm
  • Drain

Not every surface uses this ballast, and not every court is laid in the same area. Some areas have better natural drainage, different soil, no need for textile sheets to prevent weed growth etc. which all affect how a court plays.

At the recreational level, clay courts are laid in a variety of ways, usually to reduce maintenance costs. For example, in Europe, the Red Plus system is prevalent, which uses multiple layers of filled carpet offering the same playing properties as a traditional clay court. 

Why Do Tournaments Use Different Tennis Balls?

Wilson Us Labs

The reason tournaments use different balls is purely down to sponsorship reasons. Tournaments are free to strike deals with whichever suppliers they wish.

The Australian Open signed a deal with Dunlop in 2018 for them to be the supplier of the Australian Open Ball, cutting ties with Wilson who had supplied the ball for several years.

Although all balls used on tour have to have a level of uniformity, and consistency in performance. They do play differently; some are lighter, some have different felt, some fluff up more.

This changes their speed through the air, how much moisture they absorb, their durability, and how they react with the strings. Several players believe changing balls between tournaments can lead to injury.

How Often Do Tournaments Change Surfaces and Balls?

Slazenger Wimbledon Ball

Most contracts for surfaces tend to run at around the four or 5-year mark and are renewed in most cases. Decoturf, for example, was used at the US Open for 41 years before they switched. 

Balls do change slightly more frequently, and this is usually because of player feedback and tournaments often change when the minimum contract term is over.

Take the French Open ball which was supplied by Dunlop until 2011, it then changed to Babolat which wasn't too well received from the players but they stuck with it. However, Wilson is the new provider of Roland Garros tennis balls from 2020 onwards.

On the flip side, Slazenger has been the supplier of the Wimbledon ball since 1902, probably the longest partnership deal in the history of any sport.

Got any questions or points of view about court surfaces, the speed of the courts or the balls in use? Let me know in the comments.

Jonathan

Huge fan of Roger Federer. I watch all his matches from Grand Slam level right down to ATP 250. When I'm not watching or writing about tennis I play regularly myself and have a keen interest in tactics, equipment and technicalties of the sport.

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47 Comments

  1. Good article, Jonathan. The sad part is, as we’ve all discussed, the courts are way slower and our man’s success on tour suffered because of it.
    Having different court speeds throughout the year makes things way more interesting. Too bad that doesn’t happen.
    At this point in time, the courts could all be deserted and wild animals have taken over.
    One question I do have, only 1-2 mm for red brick dust? Seems not enough? Wasn’t the original clay from flower pots?

    1. I believe that they originally covered the courts (grass at the time) in terracotta dust so that they wouldn’t wilt in the sun, and it changed the court speed and bounce. They figured it out and changed it to all clay as a new surface.
      I don’t remember where I read this, and it could be a figment of my imagination and or a fake story I read somewhere. Don’t know how true this is but still a cool story

      1. Makes sense so it will be true. I didn’t know it was done to cover the grass initially ( I thought they had just put a whole new surface down as a test rather than adapted grass.) but I know they discovered it because the grass was impossible to maintain in the South of France.

    2. The courts are definitely slower. In some ways, Fed has profited from it though as well, so it’s not totally bad for him. I just think there should be a mixture irrespective of who it benefits just to keep it interesting.

      Yes, I think they were made from terra cotta pots by the Renshaw brothers then they changed to crushed brick.

      And ye there is only 1-2mm of brick dust, the underneath is limestone, but it takes on the colour the dust which is why you think there is much more of it. If there was more of it, I think the court would be completely unstable and slippery with even more bad bounces.

  2. I also thought that the brick dust layer was thicker. After a heavy shower the white limestone can show especially if the court maintenance is poor.

    About tennis balls, I’m very curious about the outcome of the following, since I never got to talk to the customer: every year my company produces and sells several tens of tonnes of yellow acrylic fiber (whose colour was matched by yours truly) for Penn USA. I have no idea whether the balls made it to the professional tour or if they are only for recreational use. But the samples we got feel nicer that the standard polyester felt. Needless to say, most of them have vanished from the show room…

  3. Thanks Jonathan.
    First, I don’t know why this year’s AO is considered Medium-fast, it was slower than ever. Also, the Court Pace Index says that in 2016 the surface in London was measured 40.6 in one image and 42.1 in the other one, what the hell.
    I agree with you, diversity is the key and it was like that in the 2000s. Or at least we need seasons with a specific set of court speed (Medium for Australian Tour, Slow for IW-Miami, Fast for US Open tour, Medium-fast for Finals, etc).

    In my club we used pure brick dust.

  4. Please.
    Could anyone help me.
    Where can I find these numbers… for instance, is there an official information at the ITF website that shows me the speed of US Open surface?

    Thanks

    André Lemos

    Typing from Brazil

    1. The speed ratings are in my table above.

      Only CPI from Hawkeye will tell you how fast a court is, and seen as though the courts have yet to be laid or played on in NYC, nobody can say how fast they are.

      It’s also tricky to discern anything from the CPI because there is no baseline measurement to judge it against or any real idea of how much 1 point in speed makes. So how much quicker is a 35 CPI vs a 36 CPI? It’s a pity there is no historical data to compare against.

  5. Wonderful article, Jonathan. As Fed Fans I think that the news of a new surface in US, let alone one which has already seen the Maestro winning in similar conditions (newly introduced in Miami, tournament dominated after the Albot scare), would be optimal for us in a normal world. Sadly, I think the chances of seeing US Open starting this year are getting lower by the day, due to the extreme Coronavirus situation in the US (not only there, of course, but damn were they hit hard by it…)

    1. Thanks. Miami was always played on Laykold at Crandon Park too, so not really a new surface for Fed. Just different colours and will play differently of course. But as I say in the post, these surfaces can be tweaked so easily that their playing characteristics change greatly.

      The USA hasn’t actually been that hit that hard. Unfortunately, the reporting around it has become so political that you cannot take anything seriously. I mean when their tv channels are using footage of Italy and trying to pass it off as the USA, something is very wrong.

      If you look at the data: https://twitter.com/FScholkmann/status/1245742543121387520

      Then it is not the number of infections that are rising. It is the number of tests that are increasing, and the infection rate is staying at a very constant rate. A sign that this not some out of control viral epidemic.

      But no outlets will report it that way. They will report cases and death count with absolutely zero context to spread fear.

  6. Many thanks for this. Yes, I know it wouldn’t be new for Roger, but I am confident about the fact that he’s usually the best in adaptability.
    For US I didn’t know, I am following very closely the situation in Italy and now numbers are constant but tests are greatly increasing. But it’s more rare to know that also here, so I thank you for this. BTW did you build an opinion on if and when the other two GS (aside from Wimby) will be played?

    1. I think the US Open might be played on schedule assuming they don’t make an early decision. My own opinion is that this thing will die down relatively quickly if the data shows its not the pandemic of the century and fear stops making decisions. I could be wrong and it is a real problem for a long time but what I am able to piece together tells me it’s not.

      Are you from Northern Italy? They have had a very bad time of it. It is like that Swiss cheese model where so many things came together and caused so many problems. Not just the virus itself but number of beds, admitting people too readily that created an environment where it spread like wildfire including to health workers. And they were also a bit slow to act. Instead of laying out a plan they were telling people to hug a Chinese person.

      One thing I have heard that seems to go unreported is that there was a mass exodus of health workers from Romania etc that just left the country immediately to go back home when the virus landed. Is that something you have heard in local media?

      It’s not all bad news though, although Italy is shown as the example of how bad things are, it’s not the whole of Italy, just a certain part. So it could be much much worse. I saw today Treviso showed that the number of deaths in their area was no greater than previous years. Despite having 100 Covid 19 related deaths. That is a good sign and shows it is manageable and excess mortality is not rising.

      1. Thanks for the very detailed reply. I live in Ticino, at the boarder between Switzerland and Italy. so I am superclose to Northern Italy, particularly the region of Milan. And I agree with you (I followed very closely the pandemic here because I am a soon-to-be Ph.D in Neurobiology, and I have some plans to continue my activity with relationships between pathogenic infections and neurodegenerative diseases), the problem was more logistic than related to letality. From a molecular and biological point of view the virus is not the end of the world, the big problem is the transmissibility, but it enhances, as you correctly stated, the logistic problems (beds for ICU, as an example). And I fear it could be the same for US, as I don’t know how much they are covered, particularly having a very different model of Assurance compared to us here.
        I heard of that exodus, there was also a massive one from the North of Italy to the Southern part. Luckily the governors in the South were very extreme in the containment measures so the problem was more or less contained.
        And so I get it is the same problem in US, some parts are really affected, some are not, right?
        Let’s really hope this nightmare gets solved soon. I’d say that, today, I would think that US Open won’t be played in September, but I like your optimism and I do hope my feelings are wrong!

      2. Ah cool, there seems to be an increasing number of scientists that are questioning some of the decision making now.

        I am not a scientist but I can always look at the bigger picture & think logically. So many of these numbers and extrapolations are ridiculous but they are getting shared so readily.

        It surprises me that so many people in positions of authority are happy to spread misinformation and cause alarmist responses. When you see Dr Fauci saying that corona is 10 times more deadly than the flu. That is complete speculation, it could be 50 times more deadly, or it could be half as deadly. Nobody has any credible data to make that determination.

        I also do not like Doctor’s or Nurses sharing individual stories and the media highlighting single cases. It leads to panic every time.

        The US has around 36 ICU beds per capita. It is said Italy has 12.5 but I am not sure if the Lombardy region had that, even if they did, they are usually at 90% capacity at this time of year so it was easy to see how they got overwhelmed when things happened fast.

        I think many parts of the USA are fine. New York is said to be the epicentre, but some citizen journalists have been visiting hospitals in NYC to see how overrun they are, and finding they are not struggling at all.

        I mean look at this, this was portrayed by the mainstream media to be a hotbed for corona patients https://www.youtube.com/watch?v=cNVTNNmurgA but clearly it’s not out of control with people flooding the hospital to get tested. I assume that channel is probably tilting towards conspiracy theories but I like the fact people are actually going out and seeing for themselves if these places are dealing with patients on the street.

        CBS News got caught using footage of an Italian hospital and trying to pass it off as NYC. That is so poor. Spreading fear can also lead to lives lost.

  7. Just one thing. Fauci is probably right in saying that it’s deadlier than flu, as in the Diamond Princess the mortality was indeed around 1 % and it was a close, randomized environment where you coul really control who had the virus and who hadn’t. It is a perfect epidemiologic situation for the researchers. So it’s likely he’s right (and btw as a scientist I followed him, he tends to be really good). But the main problem is indeed the transmissibility rather than the mortality rate, as it can load the ICUs with the heavier manifestations, even though they are a small percentage.

    1. For the rest, “good” to know that media spread panic all around the world … Thanks for your witness

    2. “10 times more deadly” is not a good statement to be making when the data is not there or backing it up.

      This wasn’t the perfect situation for epidemiology. The average age of passengers on the Diamond Princess was around 65 years old. A small sample size, just a couple of deaths, and they were all above a certain age. It is a huge bias.

      If you adjust for the age difference etc to try fit the Diamond Princess to the general population. then the mortality would be way under 1%.

      1. But it was closed, hence the good thing for epidemiology. I heard about the average age but I didn’t know the exact age, I’ll check, thanks again. Then again, you shouldn’t say that 700 people is a small sample, in my opinion. Being in the field, I would say is good enough.
        I think he didn’t overexagerate it much

  8. https://www.forbes.com/sites/victoriaforster/2020/03/22/what-have-scientists-learned-from-using-cruise-ship-data-to-learn-about-covid-19/
    I checked. According to the article the average age is 62, with people ranging from 25 to 93, and they saw that 3 people out of 4 didn’t show symptoms in the pool they tested more specifically. So the mortality, was also taking into the account that proportion of asymptomatic people, and this means that the registered mortality in the world (around 5 %) would probably go down a lot, but going down around 1 %.
    I swear I have nothing to do with Fauci but I sincerely think he’s right

    1. I honestly think corona could be the reason that science loses respect globally.

      If the average age is 62 and the mortality rate was 8 from 712 patients, the mortality rate was around 1%. But it’s not a representative sample due to the age bias.

      Surely you can’t think that discounting asymptomatic people from mortality rate statistics is a good idea?? I can’t believe I am reading that to be honest. Where in the world is that standard practice?

      You certainly need to distinguish between asymptomatic infections vs those that require treatment for assessing demand on health care systems. Which again, nobody seems to have done. But excluding them from mortality? 😆 wow.

      1. No my friend, you completely misunderstood my post. Actually I was COUNTING asymptomatic people into the mortality, assuming they are 4 times more than what we detect normally. Which is of course an estimation. But hence the numbers given by Fauci. And the sample is indeed representative, despite the average, because you can nonetheless have a number that represents all the classes of age that we need, and normalize the data of deaths. People would die to have such a sample, even though it is not normally distributed. I hope it is clearer know, I understand it is not so easy to understand but I hope you got it now (or that I was clearer)
        BTW I am not explaining my POV, Just why you can’t seem Fauci’s observations as thoughtless. In my opinion you are not that far from the truth, but surely (at least IMHO) he’s closer than you.

      2. Just to be even clearer, the mortality now is 5 % but it is VERY likely (as you also assumed) that many people were escaping detection. As usually the tests are not run on asymptomatic (at least here in Italy and in Switzerland, but I fear it’s the same everywhere for the cost of the test) and they seem to be 75 % of the infected people in reality, you could assume that the mortality becomes 1/4 of what is actually registered (so I was indeed counting all the infected people). And that is what led to the (shared) observation that the mortality is around 1 % indeed.
        I hope now is clearer Jonathan! 😀

      3. https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30243-7/fulltext
        This is the latest study on a Lancet sister journal, which also accounted for slightly less than 1 % but not by much, taking into the account also an estimation of how many asymptomatic people really are out there (which was the complete opposite of what you understood, and I apologize for that if I wasn’t clear enough) and more importantly, all the classes of age like I explained (which was also done before, even with not normally distributed samples)
        Anyway if we are too much off topic we can obviously continue this discussion privately, as you wish. And I apologize again for making you misunderstand my post.

      4. Ah ok. yes I misread, I read it as though you wanted to exclude people with no symptoms. I thought you were saying the death rate on the diamond princess was 5% if you excluded asymptomatic cases. Which it would work out to. But you meant worldwide deaths are at 5%.

        If you use the 1% death rate on the Diamond Princess and try to project it across an entire population of the USA accounting for age for example, then it is way under 1%.

        I am not saying Fauci is wrong and I like him too, but to say 10 times more deadly is surely misleading? He could just say, we are dealing with something that looks like it is more deadly than influenza so we need to be careful.

        With the 5% global stat, you start delving into died with and died from. The reporting is all over the place unfortunately. Why has nobody done the study below:

        10k people who had another respiratory / covid disease and no underlying conditions. And 10k people who had SARS COV 2 and no other conditions. Then you can judge the true mortality rate and it’s comparison to similar illnesses.

      5. I get your point of “no numbers until they are sure” as you also were coherent on your statement on media possibly spreading fear.
        And I share your view, as I said “probably” he’s right, but also I have my fair amount of doubts. Mainly because of the asymptomatic, which could be 3-4 times more than the detected ones (as it seems) or even muuuuuch more (as the Imperial college, as an example, thinks).
        And the study you describe could be useful, but the fact is that people rarely die from Co-Vid19 alone. It is the same for the flu but with (probably) even a lower death rate, but the mortality of flu also takes into account cases in which you didn’t have just flu (sadly I know it for experience, my granddad died a few months ago like this). So the “true” mortality would go down for both of them as they are both usually not so strong to kill by themselves (but not always). Hence the confusion, as you also reported, of people dying due to Coronavirus or with the Coronavirus.
        Very nice discussing with you by the way, I am truly enjoying it 😀
        (If there are some typos I am writing from my phone)

      6. I guess I should stress, I am not trying to say this thing is harmless or doesn’t exist. It is out there and can kill people.

        But are the lockdown measures commensurate with the risk of COVID 19 to most people?

        It seems that there are quite a few other diseases out there, that based on this response, we should also lock down for.

        Part of me thinks, if this disease had not been identified, it would be largely unreported in the media and the only people talking about it would be scientists and doctors who believed 2020 was a pretty bad year for flu but not something completely different to what they have seen before.

        I think real science loses out with a lot of the way these things are reported. Politics and science have collided too much.

      7. Yes, I heard about Iceland. And yes the report are below 1 %. Though for example the New England Journal of medicine stated again 1 % more or less
        https://www.nejm.org/doi/full/10.1056/NEJMoa2002032
        So the fact that probably brings governments to decide for “extreme measures” is that most likely many reports estimate that:
        1) the mortality rate is “so high” that it can’t be just a bad flu.
        2) (and probably even more important) the load on ICU is simply too much.
        And I think, particularly the second, COULD be something unprecedented.
        So if you ask me “Is it measured to what truly the disease is?” I wouldn’t know with certainty. But I would understand why people want to take stronger measures, even though I get your points as well

      8. The ICU thing is looking to be false though, as the load on them is not high at all. Northern Italy had so many factors that caused it, but other areas of Italy have ample ICU capacity. In Switzerland, certain Cantons have no patients to deal with https://www.engadinerpost.ch/2020/4/04/Engadiner-Spitaeler-haben-freie-Kapazitaeten Germany is the same.

        That is one area where asymptomatic cases should be excluded. These models are assuming 5% of all cases will need an ICU bed, but that total cases number includes the people who will not show symptoms (and will not need medical care)

        https://twitter.com/NikolovScience/status/1246823479820693505

        The numbers so far look to have been grossly overestimated. It all points to poor decision making from bad data and a fear of being negligent when one country moves first. Plus a failure to look at the costs elsewhere, all the patients who have had operations cancelled, others who are scared to go to the hospital that should go. Plus the economic impact of it all.

        I do believe it could be a case study of how not to handle a disease of this nature.

    2. I don’t know Jonathan. In Italy and Spain the situation is critical, I know that for sure. You are saying me that in New York is not the same as they describe, and I trust you, but the real thing is…. Would the absence of any measure make the situation even more critical? It’s very difficult to say no.
      BTW you reported the situation in Engadina which is just a part of Grindelwald, not that big. In Ticino the situation, as an example, is worse. But you pointed out something interesting about Germany, which was having a lot of ICUs from the start. I think that this should be a lesson for everyone NEVER to spare on health expenses. Regardless of what anyone thinks about the pandemic, I think this situation speaks volumes of how badly you’d face a situation like this in countries where health expenses were cut (like Italy, I know that all too well)

  9. Hey all, what’s up?? Long time no hear and no see. How are you all?? Safe and missing Roger?? I know I am… well atleast the second part. For me, Tennis stopped at the SF AO 2020 when Roger was in the 1st set 5-2 up against Satan 🙂 That was where it ALL ended. Ofcourse in February there was still one day of tennis with that exho where I for the first time saw Rafa… tired. Who knew that that could happen. My apologies to the Rafa fans here, but I HAD to go there 🙂 Oh and yes… I saw my Berdy there 🙂 After that…literally NO ROGER NO TENNIS 🙂

    Yesterday Eurosport 1 showed Roger’s match against Tennys Sandgren. I watched from the 4th set TB and still to date.. I still don’t know HOW Roger saved the 5th MP, the one that got him to 6-6 all in the TB. If you guys have the opportunity to watch it again, just hear the roar of the crowd after it. Even Roger looked up at all the noise 🙂

    Speaking about Roger… winning Olympic Gold at age 39 is doable… so lets all relax… The Goat got it 🙂 Love unshaved Roger 🙂 I think more of us do 🙂

    On a serious note I hope you all and your loved ones are safe during Corona times. Me, this is the third week that I am working from home. Very doable, but I miss the interactions with my collegues. I think you all do too. Please stay safe, we all have a lot of ROGER-WINS to look forward too and to discuss and we have a lot of shaved/unshaved handsome Roger to look at in the future… even if his beard is beginning to look grey 🙂

    Ps: Jon, good article… wayyyy above my head 🙂

  10. There are a ton of errors in this article. CPI and CPR also has a lot of inherent error and assumption in the perception that a sufficient number of variables are covered adequately by these man made procedures. “Feel” still plays a very important part. And some simple knowledge of chemical + mechanical structures in courts and balls goes a long way. Always climate is involved. Lastly, there are many differences in clay courts and grass courts as well. A lot of variables that you have overlooked. *ps- Laykold was originally a leading asphalt company. Lay Cold refers to laying cold asphalt as opposed to the dangerous laying of hot asphalt which was originally used long ago. Laykold acrylic is more flexible pliable and durable than decoturf. More conducive for rubber granules providing cushion. But decoturf was the leading edge of professional hard courts. The first Variable Hard Court. In 2011. Due to its unique sanding. A unique arrangement of acrylic layers with Angular SubAngular and Rounded silica which provided the most variety ever seen on Hardcourts. You could play it like a clay-court or a grass court or anything in between. It was also very suitable for the Wilson US open tennis ball and the New York climate. Laykold does not do well with the larger angular silica and is limited in its variety of sanding. It is generally a lower but less explosive bounce. Slow or fast depending on the amount of sand used but tending toward more offense without the higher bounces. Though it’s more receptive nature can also help a defensive player. If the sand stays. But again. This product doesn’t hold the sanding as well as Decoturf. Thus some slippage as well near the end of the event and possible quicker speeds

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