One of the more reliable indicators of which NHL team is likely to get the next power play has little to do with score or style of play. Instead, it’s been shown repeatedly (Ex 1, Ex 2) that referees call a substantially higher number of make-up penalties than would otherwise be expected in order to maintain an overall even number of violations on each team. Call it a biased impartiality – in order to appear impartial by game’s end, ref’s let previous decisions drive future ones.