Is Serena Williams Taking Advantage of a Weak Era?

tl;dr: No.

Serena Williams is, without question, the best player in women’s tennis right now. She’s held that position off and on for over a decade, and it’s easy to make the case that she’s the best player in WTA history.

The longer one player dominates a sport, the tougher it is to distinguish between her ability level and the competitiveness of the field. Is Serena so successful right now because she is playing better than any woman in tennis history, or because by historical standards, the rest of the pack just isn’t very good?

As we’ll see, the level of play in women’s tennis has remained relatively steady over the last several decades. While there is no top player on tour these days who consistently challenges Serena as Justine Henin or peak Venus did, the overall quality of the pack is not much different than it has been at any point in the last 35 years.

Quantifying eras

Every year, a few new players break in, and a few players fade away. If the players who arrive are better than those who leave, the level of competition gets a bit harder for the players who were on tour for both seasons. That basic principle is enough to give us a rough estimate of “era strength.”

With this method, we can compare only adjacent years. But if we know that this year’s field is 1% stronger than last year’s, and last year’s field was 1% stronger than the year before that, we can calculate a comparison between this year’s field and that of two years ago.

Since 1978, the level of play has fluctuated within a range of about 10%. The 50th-best player from a strong year–1995, 1997, and 2006 stand out–would win 7% or 8% more points than the 50th-best player from a weak year, like 1982, 1991, and 2005. That’s not a huge difference. One or two key players retiring, breaking on to the scene, or missing substantial time due to injury can affect the overall level of play by a few percentage points.

The key here is that a dominant season in the mid-1980s isn’t much better or worse than a dominant season now. Perhaps Martina Navratilova faced a stiffer challenge from Chris Evert than Serena does from Maria Sharapova or Simona Halep, but that difference is at least partially balanced by a stronger pack beyond the top few players. Serena probably has to work harder to get through the early rounds of a Grand Slam than Martina did.

Direct comparisons

So, Serena’s great, and her greatness isn’t a mirage built on a weak era. Using this approach, how does she compare with the greats of the past?

Given an estimate of each season’s “pack strength,” we can rate every player-season back to 1978. For instance, if we approximate Serena’s points won in 2015 (based on games won and lost), we get a Dominance Ratio (the ratio of return points won to serve points lost) of 2.15. In layman’s terms, that means that she’s beating the 50th-ranked player in the world by a score of 6-1 6-1 or 6-1 6-2. The 2.15 number means she’s winning 115% more return points than that mid-pack opponent. If the pack were particularly strong this season, we’d adjust that number upwards to account for the level of competition.

Repeat the process for every top player, and we find some interesting things.

Serena’s 2.15–the second-best of her career, behind 2.19 in 2012–is extremely good, but only the 21st-ranked season since 1978. By this metric, the best season ever was Steffi Graf‘s 1995 campaign, at 2.42, with Navratilova’s 1986 and Evert’s 1981 close behind at 2.38.

Graf has seven of the top 20 seasons since 1978, Navratilova has four, and Evert has three. Venus’s 2000 ranks sixth, while Henin’s 2007 ranks tenth.

It seems to have become harder to post these extremely high single-season numbers. In the last ten years, only Serena, Henin, Sharapova, Kim Clijsters, and Lindsay Davenport have posted a season above 2.0. Serena has done so four times, making her the only player in that group to accomplish the feat more than once.

Best ever?

As we’ve seen in comparing Serena’s best seasons to those of the other greatest players in WTA history, it’s far from clear that Serena is the greatest of all time. Graf and Navratilova set an incredibly high standard, and since the greats all excelled in slightly different ways, against different peer groups, picking a GOAT may always be a matter of personal taste.

Assigning a rating to the current era, however, isn’t something we need to leave up to personal taste. I’m confident in the conclusion that Serena is not simply padding her career totals against a weak era. If anything, her own dominance–during an era when dominating the women’s game seems to be getting harder–is making her peers look weaker than they are.

7 thoughts on “Is Serena Williams Taking Advantage of a Weak Era?”

  1. Interesting as always. Of course, as you observe, the pleasure of this sort of debate among fans is to cherry-pick the data so as to champion a personal favorite while disparaging other GOAT contenders. Second-best pleasure is to claim that the differences between eras in terms of technology & training render comparison impossible. And then sneak in your personal favorite anyway.

    I am curious if you’ve done a similar piece on the ATP. I used Google to search within the heavytopspin.com domain for a comparable piece but didn’t seem to find one. There were pieces like the one about Djokovic’s year-end run in 2013 etc. but not an overview as such. Meanwhile the WTA previously got overview attention in your piece “The Changing Depth of the WTA.”

    If you can point me to some good pieces on ATP depth that you’ve done, and that my search missed, I’d love to go back & read them; otherwise may I suggest such a piece if you get the time? The prevailing assumption is that once Djokovic re-invented himself a few years ago & he and Nadal started jousting, the last few years at the top have been brutal; but that does not address the rest of the field; nor does it address the bickering among fans as to whether Federer enjoyed a weak era or not (I searched for “Federer” + “weak era” and didn’t get much on that, either).

  2. I wrote something using similar methodology about the ATP for Tennis Magazine last year. I don’t think it’s online. It was recently cited and described a bit here:
    http://www.economist.com/news/international/21657818-everybody-knows-todays-sportsmen-are-better-their-predecessors-working-out-how?frsc=dg%7Cc

    The conclusion was very different — it showed that the level of play has steadily increased over the decades, a little bit almost every season. I had to change a few parameters for this study, because of the differences between ATP and WTA data; I need to take a closer look to see if that’s why the results were so different.

    Anyway, re: ATP, my finding was that the improvement in field level was so great that the best player right now is, by that measure, the best of all time. “Right now” depends on your time-scale preference — a 10-year peak gives you Fed, a 5- or 7-year peak (when I wrote it, 18 months ago) gave you Rafa. I suspect if I re-ran the analysis right now, a 5-year peak would give you Novak.

    Still, the tough question is how to measure competition at the top — when most pundits talk about era strength, they’re really talking about whether there was a small number of highly competitive players. But “small number” is the kicker there–how do we compare, say, Sharapova as Serena’s foil to Evert as Martina’s foil? What if Maria is statistically as good, but the H2H is still a disaster for her? GOAT debates are murky territory indeed.

  3. Thanks for the link. Interesting read – the Economist is a clever publication – like TIME in a way, being written for a large audience, but quite smartly written where TIME tends to dumb down. But even the Economist has its formulas & because they refuse to byline their pieces, and also precisely because the writing is “clever,” I find it difficult to judge fact from fiction when I read them. This particular piece makes some nice points in passing but because it is such an amalgam of sources it struggles to do anything more than that. Yet by putting your analysis at the end as a “capper,” it does seem to raise the question of, why has tennis seen more of a jump in overall improvement than some other sports? Ah well.

  4. Imagine how much fun this would be if we actually could get all the WTA match stats! I checked the WTA web site the other day and they don’t even have the basic 2015 match stats for Bouchard, although they are there now (frequently the stats for top players either “blink out” or are just randomly included).

    I’m curious how you derived the approximate game score from the dominance ratio.

    1. Yeah, would be great to have WTA stats. For this purpose, though, I don’t think it would make much of a difference.

      I took the matches for which I do have stats, and derived the (very approximate) relationship between percentage of games won and DR.

  5. Quite frankly, from a scientific point, I don’t agree with the analysis for several reasons. One, it was assumed that Serena Williams would have a harder time going through the draw in the earlier rounds today as opposed to 10-20 years ago. It’s an assumption that may not be true. And most likely flawed. Rarely do players outside the top 16 win majors. In fact, since 2000, in the WTA, only 1 player outside the top 16 has won a major. Serena was ranked #81 at the 2007 Australian Open when she won. (We see in the ATP, Goran Ivanisevic or Marat Safin won from even lower rankings). Therefore, depth of the field is not a factor since no woman outside the top 16 basically have a chance of winning. Recently, we witnessed an aging population of tennis professionals and there are several questions being asked. Second, sports medicine and science are far more sophisticated today than 20 years ago which can contribute to longer playing careers of dominant athletes. That can skew some data towards the better players. Third, we know the pay scale for WTA and ATP is heavily skewed away from younger players. It takes 5-6 years for a promising player to break the top 100 (if they turn pro at age 17-18). Again, data is skewed towards better players simply because the younger players, even if they would be good enough are slowed by the current tournament tier systems. Fourth, there is a growing epidemic of obesity and lack of activity and de-emphasis on physical education. This factor contributes by decreasing the incoming age groups in competencies. There are several studies showing that young athletes are not at the level of young athletes maybe 40-50 years ago. That’s why many trainers are getting business since youth players rarely train naturally anymore. Although this has only been recently noticed, it might be a factor for those born after 1990 in the modern personal computer age and obesity epidemic. One can argue athletes are active and this has nothing to do with inactivity, but keep in mind the pool for prospective professional athletes may actually decrease even if the overall population increases. Hence, we didn’t see many teenage players in 2013-14. We do see a few now but in part due the aging of many touring pros. France Italy, and Spain for example, have more than a few pros (ATP and WTA) in their mid-30s. Federer and Serena (and Venus) are not the only aging athletes.

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