Bob Speed sends me an email from Australia with the following observation:
Since penalties were introduced into the European Cup/Champions League, 10 finals have gone to extra time. Nine of those games have proceeded to shoot-outs, with 1 goal being collectively scored in those 10 extra times (of 30 minutes each). That's 300 minutes (the equivalent of 3.33 games) of soccer with 1 goal being scored. Small sample size I know, but eye-opening.
Before penalty shoot-outs were introduced into the competition, 4 final games went to extra time. Three of those produced a result. The one that did not was replayed (as was the rule back then).
The strategic equilibrium, I think, is to sit back and defend while pouncing on any mistake your opponents make. The Italian game follows this script more than any other, and the 0-0 draw between Milan & Juventus in the 2003 final -- a pitch loaded with wasted skill!! -- epitomizes the problem. What is not clear to me is why moving from replays to penalty kicks increases the tendency to play for a draw. For equally matched teams, both methods are a coin flip. In the case of replays from yesteryear, it may be that the players wanted to finish the job on the night in order to start their vacations. This could break down strategic discipline, particularly in light of the fact that fully compensating players for replays would distort incentives.
Although the mechanism may not be obvious in this case, there is no doubt that incentives affect strategic choices made by managers. A change in incentives in the NHL clearly led to an increase in tied scores after three periods. Jeff Klein at the NYT's Slap Shot blog gets into the details, with some observations from yours truly.