Measuring Possession

By Lou Burruss
publicado en: http://skydmagazine.com

‘Possession’ gets thrown around a lot without a clear understanding of what it means from an analytical standpoint.  A big part of the issue is one of vocabulary; we generally lack good terminology to describe the various attributes of possession.  One way to facilitate thinking  is to pull a concept apart, breaking it into more well-defined pieces.  Because the discussion and thinking around possession is still evolving, the names for these pieces are drifting.  These are the ones I use; you may have heard something different.



Efficiency  ( = goals scored/possessions)

This is the most useful of stats for predicting victory.  Because ultimate is an alternating possessions game and each point is only worth one, the team that is more efficient wins.  Period.  By definition, that crazy-throwing karma team is more efficient than the steady dump-swing team, if they win.  Efficiency is a really useful stat for setting team goals.  It is also a really helpful way to think about possession above the pass level.  Steve Moons was the first person I heard really articulate the idea of a “win-line” – the efficiency percentage you must reach to win.  For Club ultimate in the 90s, Steve put the win-line at 60%.  If you were more efficient than that, you’d almost always win.  In the last decade or so, it may have crept upwards slightly, but only slightly.  For reference, I’d put college men’s and women’s club at 50% and college women’s at 40%.

Retention (= passes completed/passes attempted)

What is nice about retention is that you can really focus in on an individual’s performance.  If you have the luxury of filming every game and the time to digest all that film, over the course of a season you can get a really good statistical look at how individual players are performing.  Like all statistics, don’t read too much into a single game; there just isn’t enough data.  If you want to look at a single game, you are much better treating it as a case study than as statistics.  A final note: a retention number below 90% is abysmal.

The biggest danger of retention is that you confuse it with efficiency.  The goal of ultimate is not to complete passes, but to score goals.  Completing passes is a necessary but dangerous requirement to score goals.  All too often, teams focus on completion instead of conversion.  Claiming they are a ‘possession’ team, they are frustrated in losing to a team that is a lot less ‘disciplined.’

The calculation of this statistic is a little tricky on the ends.  How do you count a dropped pull or a dropped goal?  The clearest way I have seen is to count an individual’s ‘pass attempt’  as being with a catch and ending with a successful throw.  The goal catch becomes a ‘pass attempt’ with no pass but counts for that person’s retention.

Conversion (= goals scored/points played)

In a way, this statistic is almost meaningless because it is right there to see in the final score of any game.  It does have its uses though, particularly if you are playing O-line and D-line.  It allows you to segregate the data into those two groups and take a look at how each has performed.  Club teams typically shoot for a 70+% O-line conversion and a 30+% D-line conversion rate.  (As long as your O-line + D-line conversion totals more than 100%, you win.)  This sets up a wonderful staple of club team practice – the 10 pull.  Defense pulls ten times, not trying to win, but just beat their conversion goal.  Only 2 D goals?  Offense wins.  Four or more D goals?  The defense.  Finishing the scrimmage 7-3 is a push.

Another area conversion is helpful is in terms of overall team strategy.  For a possession oriented team (like DoG or Revolver) focusing on efficiency is a really useful goal.  However, for a less possession oriented team (like Doublewide) it is often smarter to focus on conversion.  Taking chances the way they do, they know they are likely to turn it over.  The focus no longer is solely on possession, but a more holistic approach to scoring that emphasizes defense and smart risk taking.