I understand that this should be something like ratio of power play goals and total number power plays. I wonder whether in some cases the fact that the power play is shorter than 2 minutes is factored in when calculating PP%.
There are several reasons why power play might be shorter, here are some I can think of:
- The power play ended because a team scored a goal.
- The power play was shorter because a team playing power power received a penalty.
- The power play was shorter because the penalty of the opposing team was called while playing shorthanded, which means that there was 4 on 4 play before the power play stared.
- The power play was shorter because it started less than two minutes until the end of the game.
In the first case, this was a successful power play - so there is no doubt how this should be counted. In the second case, it is the mistake of the team who had the advantage that they infringed the rules. So it should be counted an unsuccessful power play and the fact that it was shorter does not seem to be relevant. Probably the similar argument can be in the third case.
But at least in the fourth case we can say that it is not the team's fault that the power play they played was shorter. So the team has less time than 2 minutes to score a goal in the power play. So it seems a bit illogical that if they do not score this should be called in the same way as if they do not score during the whole 2 minutes.
In any case, what I wrote above are just my speculations. I would be glad to find some official source showing how this statistic is counted in these special cases.