Wednesday, July 14, 2010

Does Soccer Have a Scoring Problem?

Bain had a thoughtful comment on an essay in the Wall Street Journal titled Soccer's Scoring Problem.

"Great essay from an econ prof about randomness in sports. I’d never thought of sports this way before, but it’s true that basketball and tennis have so much scoring that an underdog victory isn’t worth waiting for, and hockey/soccer have so little scoring that a single blown call or brief burst of good fortune usually determines the outcome.

The author posits that baseball and football toe the randomness line perfectly, and I agree."
There are a few certainties in my life when it comes to my friends and their expertises. Schweifler is never wrong about efficiency (same with Barrett) and value oriented buying, Hegarty knows everything about beverages, Addy has never been wrong in trivia, ever,  Kenna knows sensitive tunes, Walmsley knows value investing and sunday brunch, Ziser knows t-shirts and hip things, Hamilton knows alternative bands that I should be checking out, and Alex Bain knows statistics. Like really knows statistics.
So I read Bain's comment on the Soccer scoring problem and how so few goals makes soccer results too random, and I nodded my head and moved on. But then something was bugging me. We all know how scarce goals are in soccer, so I appreciate the scoring chances (shots on goal). In fact, I find shots on goal almost as exciting as a real goal. Furthermore, it seems like the team with the most scoring chances usually wins. Now, I have no idea if this is true and I did some Google searches and couldn't find anything online drawing a direct correlation between # of shots & probability of winning.  However, if you assume that goals occur at a fairly constant % of shots on goal (big assumption), then soccer might not be as random as you thought. I looked at the World Cup Final results and the Dutch had 14 Shots and the Spanish had 21 shots. Again assuming the goals are a fairly constant % of shots, then it makes sense that the Spanish would win because they had 50% more shots. Take more shots and you're likely to win. Sunday's result wasn't random at all.
Bain & Others, what do you think of this logic? I've used the results from 1 game to validate what I'm saying so it's not like I'm making an argument based in Stats, but it seems to make sense to me. Maybe someone out there with better Google skills than me can find a mathematical analysis of this very problem. I'd love to read it.