TL;DR Which Types of Partners Win Combined Ratings Doubles

Doubles Matches and Partners with Equal vs. Unequal Ratings

This and the next few posts examine combined rating doubles to determine whether certain level and gender combinations win more often than others. And, more importantly, why?

If you've played in USTA combined rating system leagues, and especially if you've captained a team, you have likely wondered whether it's better to pair players with equal or unequal ratings (e.g., a 4.0 with a 4.0, or a 4.5 with a 3.5).

And in mixed doubles, is it better for the man or woman to have the higher rating?

One school of thought is that a 4.5 player can dominate play. Others feel that a 3.5 player becomes a target for a solid 4.0 doubles pair.

To answer these questions we looked at a little more than 100,000 USTA doubles league matches played in 2016. Only matches where both doubles teams had a combined rating equal to the league rating level were included. So, for an 8.0 league, matches with partnerships of 4.0/4.0 or 4.5/3.5 were included. Any other combinations, such as 4.0/3.5, were not included.

So before we see the answers, let's get a feel for what types of players and matches were examined.

This shows that about 80% of the matches were played in 7.0 and 8.0 leagues. This makes sense since most USTA players fall into the 3.5 to 4.0 rating levels.

Next, let's look at the breakout by gender and rating level. This may surprise readers who live in a section or district that offers combined rating leagues only for mixed doubles.

Mixed Doubles is by far the most popular format for the combined rating system, accounting for about 71% of matches played. This is more clearly shown the the next chart.

Again, the questions are:

1. What combination of ratings wins more often, unequal (such as 4.5 & 3.5) or equal (such as 4.0 & 4.0)?

2. For unequal partners, does a partnership with a man or a woman in the higher rated slot win more often? That is, does a partnership of a 4.5 woman/3.5 man win more than 4.5 man/3.5 women?

We'll start to answer these questions in the next post.

Does Gender Make a Difference?

In Part 2 of this series, we looked at 2016 combined ratings doubles league matches and found that, overall, partners with Unequal ratings won about 56% of the time when playing against partners with Equal ratings. The win percentage for Unequal partners in 7.0, 8.0, and 9.0 was similar (see the last chart in Part 2).

It is challenging to write about combined rating system doubles and some terms are used that may be unfamiliar. If you’ve not read Parts 1 and 2 of this series, you may find doing so now beneficial. If you want to skip Parts 1 and 2, here are a few terms that will make this post easier to read.

Combined rating system: A system that limits the combined ratings of doubles partnerships in a doubles league. For example, if the league is identified as 8.0, doubles partnerships may be 4.0/4.0, 4.5/3.5, or 4.0/3.5. Generally, a partnership cannot be separated by more than 1.0 in level, so a 5.0/3.0 would not be allowed. And of course a 4.5/4.0 partnership would not be allowed because it exceeds the league level.

Unequal partners: doubles partners that do not have the same rating, such as a 4.0/3.0, or 4.5/3.5 partnerships.

Equal partners: doubles partners that have the same rating, such as 4.0/4.0, or 3.5/3.5 partnerships.

We now need to ask whether gender affects the results. And eventually we’ll determine how the strength of a player relative to other players of the same rating affects the results. But for now, the focus is gender.

In Part 1 we saw a chart that showed the number of Men’s, Women’s, and Mixed doubles matches that were played in 2016 by four levels - 6.0, 7.0, 8.0, and 9.0. Overall, about 71% of these matches were mixed doubles. And the ratio of men’s-to-women’s-to-mixed appeared graphically similar in each level. So, how does gender affect the likelihood of winning a combined ratings doubles match?

We’ll start with Unequal vs. Equal matches by Men’s, Women’s, and Mixed. Look at the chart below.

This chart shows the Unequal partners win percentage when playing against Equal partners in combined ratings leagues. The winning percentages across each league type are similar. And since Mixed is by far the largest group (71%), it makes sense that its winning percentage of 56.5% is very close to the overall average of 56%. So far these results are consistent with what we found in the previous blog post.

Let’s see what the winning percentages look like when grouped by doubles league rating level.

This chart shows the Unequal partners’ winning percentage vs Equal partners by combined ratings level and league gender. The overall average of 56% appears in orange.

A few observations are:

At the 7.0, 8.0, and 9.0, Unequal partners appear to have an advantage, particularly in Mixed and Men’s. In fact, the only groups where Unequal teams do not win more than 50% of the time are the Men and Women at 6.0 - this is one of the two observations that jump out.

The second observation that jumps out is that at the 9.0 level, Women’s Unequal teams have the highest winning percentage (vs. Equal teams) at 61.4%. We’ll look at why in a future post.

Our next post will focus on Mixed Doubles and whether the gender of the higher rated Unequal partner makes a difference.

Which Partnerships win more tennis matches?

So far it seems that Unequal partnerships have an advantage when playing against Equal partners. Now we’ll focus on Mixed doubles to see if the gender of the higher rated partner (HRP) makes a difference. Of course, to do this we’ll look only at matches that involved at least one Unequal partnership. If these terms don’t make sense, read Part 3 of this blog series (scroll down to find that post).

We started this blog series with a little over 100k combined ratings doubles matches at the 6.0, 7.0, 8.0, and 9.0 levels. Of those, about 72k were Mixed doubles as shown in Part 1 of this series. And we found that about 37k of the Mixed doubles matches involved at least one Unequal partnership. Next we’ll drill down to matches of Unequal vs. Equal partners. The chart below shows the split by level and by partnership type.

The chart shows that a very large proportion of Mixed consisted of Equal partnerships vs Unequal on both an overall and per level basis. Unequal vs Equal totals about 30k matches. The math and statistics gurus will like that we have a number of matches that’s big enough to give meaningful conclusions.

Before we look at the gender split of the higher rated winning partner, let’s first look at which gender is more common in the higher rated slot. We’ll check all Unequal partnerships that played Equal partners. This number will help frame the conclusion of this post.