In late 2011, I became interested in compiling data from The Hockey Summary Project in a way that might be more useful for research. In the process, I was intrigued by the idea of maintaining period-by-period data; I rationalized that, for historical data, we might be able to avoid the score effects on shot data (teams with the lead in the 3rd laying back and losing the shot battle) by excluding third period data. It’s rarely a good idea to exclude that amount of data if you don’t have to (or can adjust data), but the data available at the time (and currently, as of 2015) made this the better option. I soon found that this 2-Period Shot-for Percentage (or 2pS%) was not only a decent proxy for modern possession measurements, but also aligned strongly with measures of success and zone time. With these findings, I undertook a two-year project to compile and calculate 2pS% in a way that could provide richer presentation of the data for visualizations and researchers. Below, I have provided an example, with seasonal measures of 2pS% for teams, season-by-season, giving you an idea of how team histories of possession progressed from 1952-53 through 2014-15. By clicking on the grey “Report” bar and selecting “Filter,” you can select/de-select any number of team seasons for comparision. I have included a line indicating league-average (obviously, 50%), as well as lines for playoff-level play called “Playoff Line” (ballparked at 52.5%; established in this post) and its opposite called “Doldrums.”
If you’re interested to see what happened within one of these seasons (ex: Were the Boston Bruins that good for all of 1993-94, or did they take off at some point?), I highly recommend checking out our single season charts. We’ve also added comparison charts, where you can place individual team seasons side-by-side with other franchises’ in a variety of metrics.
P.S. Some of the limits of the display are really just the limits of the embed and WordPress. If you have an Office Online account, you can click on the bottom right icon below any of the graphs to see the data; if you don’t, you can still download the document by clicking the left-most of the icons in the bottom right.
If you need help with learning how to use the graphs, or troubleshooting, or have questions, suggestions, or data requests, please check out our tutorial.