We took the WTA top 20 and ranked them using the points system adopted by the ATP World Tour. There were some significant changes – especially at the top.

If the WTA adopted the ATP’s ranking system, Caroline Wozniacki would be the year-end No.1.

That was the finding when the Tennismash team crunched the numbers, factoring in top-20 players’ tournament results in season 2017.

According to the WTA rankings, Wozniacki finished world No.3 but under the ATP system she leapfrogged current world No.1 Simona Halep and second-ranked Garbine Muguruza to take top spot.

Halep fell to world No.3 under the ATP points system.

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There were some other notable movers including 13th-ranked Sloane Stephens, who jumped into the top 10. We also added Serena Williams into the mix to see where she’d land, and that was 16th under the ATP system, despite being ranked No.21 on the WTA list.

Here are the final standings – and below that, an explanation of how we got there.

WTA Rank ATP Simona Halep 1 Caroline Wozniacki Garbine Muguruza 2 Garbine Muguruza Caroline Wozniacki 3 Simona Halep Karolina Pliskova 4 Karolina Pliskova Venus Williams 5 Elina Svitolina Elina Svitolina 6 Venus Williams Jelena Ostapenko 7 Jelena Ostapenko Caroline Garcia 8 Caroline Garcia Johanna Konta 9 Johanna Konta Kristina Mladenovic 10 Sloane Stephens Svetlana Kuznetsova 11 Kristina Mladenovic CoCo Vandeweghe 12 CoCo Vandeweghe Sloane Stephens 13 Svetlana Kuznetsova Anastasia Pavlyuchenkova 14 Anastasija Sevastova Anastasija Sevastova 15 Madison Keys Madison Keys 16 Serena Williams Elena Vesnina 17 Anastasia Pavlyuchenkova Julia Goerges 18 Elena Vesnina Angelique Kerber 19 Julia Goerges Ashleigh Barty 20 Angelique Kerber Serena Williams 21 Ashleigh Barty

Firstly, here’s a rundown of how the ATP structures its ranking points system, taken from atpworldtour.com:

The year-end Emirates ATP Rankings is based on calculating, for each player, his total points from the four (4) Grand Slams, the eight (8) mandatory ATP World Tour Masters 1000 tournaments and the Nitto ATP Finals of the ranking period, and his best six (6) results from all ATP World Tour 500, ATP World Tour 250, ATP Challenger Tour and Futures tournaments.

There’s an addition to that – players who finish in the year-end top 30 in the previous year count as “commitment” players the following season, meaning they must count four ATP 500 tournament results in their “best six” outside of the Grand Slams and Masters events.

The WTA system has less mandatory requirements for top 20 players. They must count their results from the four majors, WTA Finals and four Premier Mandatory tournaments, and best two Premier 5 performances. The points structure differs slightly, with more points awarded for early-round losses than what’s given at equivalent ATP events for the same performance. A WTA Grand Slam runner-up gets 1300 ranking points, while an ATP major finalist gets 1200.

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We considered the WTA tournaments as their ATP equivalents. Therefore:

the Grand Slams remained the same

the WTA Finals were treated as the ATP Finals

the WTA’s four Premier Mandatory and five Premier 5 events were grouped as the nine ATP Masters 1000 events

in the “best six”, WTA Premiers became ATP 500s, and WTA Internationals became ATP 250s

The one difference was that we counted all nine “Masters” events as mandatory, because the WTA does not really have the equivalent of a Monte Carlo Masters – the one non-mandatory ATP Masters 1000 tournament. We also didn’t take into account Zhuhai results, because the ATP has no equivalent tournament. In this exercise, the “season-ending WTA Finals” is actually the season-ending event.

The players highlighted in yellow? They didn’t finish in the top 30 last season, meaning that, because they weren’t considered “commitment” players, they didn’t have to count four WTA Premier (ATP 500) event results in their “best six”. This rule hurt Pavlyuchenkova the most – she won three WTA International (ATP 250) titles in 2017, but because she was a commitment player, one of those could not be counted in her “best six” as it needed to make way for one Premier-level result. She fell three places to No.17 under the ATP system.

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The biggest difference between the two systems – and one which explains Wozniacki’s ascent to No.1 – came in the awarding of points for the year-end Finals. Under the ATP system, the undefeated champion can earn a maximum of 1500 points – 200 for each round-robin match win, plus 400 for a semifinal win, plus 500 for the final win.

It also means that should a player go 0-3 in the round-robin stage, they would walk away from London with zero points. But in Singapore? A player could lose all three of their round-robin matches and still earn 375 points – more than an ATP 250 or WTA International tournament title! – because the WTA awards players 125 points for each round-robin loss.

Under the ATP system, Wozniacki was able to make up ground on the higher-ranked Halep and Muguruza, earning 1100 more points to pip them at the post. Using the WTA system, Halep and Muguruza each earned 500 points for their performances in Singapore – which would have preserved the lead they hold – rather than the measly 200 awarded under the ATP structure.