Advanced Metrics: PDO streaks and season-long performance spreads

Here are the best and worst Shooting %, Save % and PDO over the last four seasons:

This is really intended as a cautionary tale - in both positive and negative directions. If your team is posting a 12% shooting percentage or a 1040 PDO through 10 or 20 or 30 games, you need to ask yourself if it's illusory, or if your team is the best team we've seen in half a decade. Notice that the spread of PDO is less than the spread of shooting and save percentage independently; there are a variety of reasons for this - systematic shot counting bias at various arenas, and the fact that a team that cheats on offense to score more often has to give something up on defense.

At any rate, here's the range of observed PDO over 1-82 game stretches:

The spread over a full season is roughly half as large as the spread over 20 games. So whatever you observe in a quarter-season needs to be tempered by 50%; and don't be surprised if a team riding a PDO high starts losing as they come back to earth.