Sunday, June 13, 2010

Huge "choke" effect reported in soccer

According to an academic quoted in this NYT article, there's a huge "choke" effect in soccer penalty kicks.

Gier Jordet, a professor at the Norwegian School of Sport Sciences in Oslo, reports that, when the score is tied, penalty kick shooters succeed at a 90% rate. But when the shooter's team is behind by a goal, and presumably there's more pressure, he succeeds only 60% of the time.

Wow. That's some serious choking. The effect is so large I can barely believe it.

Another effect Jordet found is that, when the game is decided by penalty kicks in a "shootout" after a drawn match, shooting percentages drop with each successive attempt:

"... 86.6 percent for the first shooter, 81.7 for the second, 79.3 for the third and so on.

“It demonstrates so clearly the power of psychology,” [Jordet] said."

That's difficult to explain too, although I suppose it could be that the team puts the best shooter out first, then the next best shooter, and so on. That would neatly account for the decline.

Still, these are both very surprising results. As always, anyone with access to the studies the article is based on, if you wanted to send along a copy, I'd appreciate it.

(Hat tip: Elizabeth)

UPDATE: Part II is here.

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At Monday, June 14, 2010 8:29:00 AM, Anonymous Dan R said...

I can imagine two reasons why the success rates decline per kicker. 1) They're aware of the choke rate, so they would structure the order that way and 2) prior misses would affect the later rate if not controlled for.

Going from 90% success to 60% due to choking would give a decline from 90% to 87.3% solely due to choke effects between the first and second kicker. I'd hope they controlled for this impact in that listing of successive success rates.

At Monday, June 14, 2010 8:39:00 AM, Blogger Phil Birnbaum said...

Ah, good point. The first part of the article says that players kick 90% when tied, and 60% otherwise. In a shootout, the earlier the kick, the more likely to be tied.

Good catch.

At Monday, June 14, 2010 9:26:00 AM, Blogger Greg Finley said...

I'm not sure if this is already accounted for, but aren't subpar teams more likely to be losing at any point of the game than average teams would be, thus giving them more opportunities to shoot in such situations?

If the subpar teams have worse penalty kickers on average, won't these kickers be overrepresented?

At Monday, June 14, 2010 9:30:00 AM, Blogger Phil Birnbaum said...

Greg: makes sense, but 60% seems like a LOT. It seems extreme to me to suggest that teams behind by a single goal are 60% penalty kick shooters instead of the 90% average.

If you said 85%, or 80%, maybe. But 60%?

At Monday, June 14, 2010 9:34:00 AM, Blogger Greg Finley said...

You're right, the effect is too large to be attributed to my point alone.

Maybe if there was a within-team analysis (i.e., how does Italy do when tied or trailing by one?), I'd be more impressed. Though, again, Italy is likely to be trailing against teams with above average goalkeepers, who are also more likely to stop penalty shots.

At Monday, June 14, 2010 9:39:00 AM, Blogger Phil Birnbaum said...

Greg: yes, indeed, a within-team analysis would help. I would love to just have access to the data, to be able to figure out what's going on myself.

At Monday, June 14, 2010 11:02:00 AM, Anonymous Guy said...

My guess: the researchers are looking only at the final kick for the team trailing by one (where miss = loss). However, the tied teams may have multiple opportunities to kick the winning goal. If they kicked at a 72% rate and had 2 opportunities on average, they would win about 92% of the time. If the researchers looked only at the game outcome, without measuring each attempt separately, that could explain their result.

You also have to consider the goal keeper here. The trailing team not only will have weaker kickers on average, they will also be facing a better defender. Even so, I agree a 30-point gap is implausible.

At Monday, June 14, 2010 11:24:00 AM, Anonymous Guy said...

Actually, I forgot teams alternate kicks, so tied teams don't get multiple attempts to win.

However, if they look only at ties where a goal ensures victory (as article says), then that has to be the 2nd team in situations where they are tied despite one fewer attempt -- so they probably are quite a bit better.

I also wonder about kicks where the trailing team could lose with a miss, but not ensure a tie (e.g. trailing 4-2 on 4th kick). If those were counted as a "miss," it would reduce success rate of the -1 teams.

At Monday, June 14, 2010 12:14:00 PM, Anonymous Guy said...

OK. The tied teams have to be kicking last, which means they are tied despite one fewer attempt. Let's say the scores look like this:
4-4 (45% frequency)
3-3 (45%)
2-2 (10%)
Then the second team is already shooting about 84%. So it wouldn't take a big choke factor (by the defensive team) to get to 92%.

Similarly, a -1 team kicking second in the 5th round is probably shooting about 65%. The -1 teams kicking 1st in the 5th round will be even a bit weaker, having had equal opportunities. So an average of 60% doesn't require a very large choke effect (if any).

At Monday, June 14, 2010 12:21:00 PM, Blogger parinella said...

Couldn't the shootout effect be explained by goalie familiarity, or by a tendency of shooters to not repeat what the previous shooter did (or to kick away from the area the goalie dove on the previous kick)?

At Monday, June 14, 2010 2:15:00 PM, Anonymous Haakon said...

I found an abstract of the study here or here. A published study, at least, though can make no comment on the methods as I can't read the full text.

Oh, and it's Geir Jordet. */Norwegian nitpicker*

At Monday, June 14, 2010 2:38:00 PM, Anonymous Guy said...

The study only includes 409 shootout kicks. That means about 80 5th round kicks, give or take, so the two samples (tied, down by 1) can't have more than 40 kicks each -- and probably a lot less. Oh well.....

At Monday, June 14, 2010 6:07:00 PM, Blogger Don Coffin said...

It appears to be a 3-year-old article. Here's a link to a summary:

There does not appear to be an ungated version lying around anywhere, not even on his website.

At Tuesday, June 15, 2010 9:38:00 AM, Blogger Phil Birnbaum said...

Sorry so late getting to these comments ... was travelling all day yesterday. Back home now, and someone sent me a copy of the study (thanks!) so I'll be commenting this afternoon.

At Tuesday, June 15, 2010 5:24:00 PM, Blogger Phil Birnbaum said...

OK, so, Guy, you're suggesting some kind of selective sampling. Like, retroactively considering previous kicks for teams who are behind.

I agree that might do it. I think that might be the *only* way, unless there's really a situation in which kickers shoot only 60%.

Let me read one of the papers that someone sent me ...

At Tuesday, June 15, 2010 5:41:00 PM, Anonymous Guy said...

I don't think accounting for the 60% in the down-by-1 group is difficult. The overall average is abut 70%. Most of these kicks are by the 5th best, or worse, kicker on a team. And if a team is down by 1 goal, they are likely to be a bit below average (especially those making 5th kick for team that kicks first).

What's much harder to explain is a 92% success rate if team is tied and goal ensures victory. They are tied despite one fewer attempt, so they are probably shooting about 80% after 4 attempts. Still, that probably isn't their true talent %. Plus, these teams are also using weak kickers for the most part. So I can't see how they shoot 92%. Perhaps this is just a very small sample size? Or could 92% be the winning % for these teams (they win 80% of the time on the next kick, plus 60% of the shootouts where they miss)?

At Tuesday, June 15, 2010 5:45:00 PM, Blogger Phil Birnbaum said...

In the study I'm reading right now, the overall rate is 82.7% in Copa America, 84.6% in the European Championships, and 71.2% in the World Cup.

Overall, for kicks 1-5, the percentages are:

87, 82, 79, 72, 80.

So 60 seems to me like it's not likely even for the worst kickers.

The study I was sent is not that one, with the 60% figure, so we still won't know ...

At Tuesday, June 15, 2010 8:15:00 PM, Blogger Phil Birnbaum said...

Part II posted:


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