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June Wins Above Expectation July 1, 2011

Posted by tomflesher in Baseball, Economics.
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Even though I’ve conjectured that team-level wins above expectation are more or less random, I’ve seen a few searches coming in over the past few days looking for them. With that in mind, I constructed a table (with ample help from Baseball-Reference.com) of team wins, losses, Pythagorean expectations, wins above expectation, and Alpha.

Quick definitions:

  • The Pythagorean Expectation (pyth%) is a tool that estimates what percentage of games a team should have won based on that team’s runs scored and runs allowed. Since it generates a percentage, Pythagorean Wins (pythW) are estimated by multiplying the Pythagorean expectation by the number of games a team has played.
  • Wins Above Expectation (WAE) are wins in excess of the Pythagorean expected wins. It’s hypothesized by some (including, occasionally, me) that WAE represents an efficiency factor – that is, they represent wins in games that the team “shouldn’t” have won, earned through shrewd management or clutch play. It’s hypothesized by others (including, occasionally, me) that WAE represent luck.
  • Alpha is a nearly useless statistic representing the percentage of wins that are wins above expectation. Basically, W-L% = pyth% + Alpha. It’s an accounting artifact that will be useful in a long time series to test persistence of wins above expectation.

The results are not at all interesting. The top teams in baseball – the Yankees, Red Sox, Phillies, and Braves – have either negative WAE (that is, wins below expectation) or positive WAE so small that they may as well be zero (about 2 wins in the Phillies’ case and half a win in the Braves’). The Phillies’ extra two wins are probably a mathematical distortion due to Roy Halladay‘s two tough losses and two no-decisions in quality starts compared with only two cheap wins (and both of those were in the high 40s for game score). In fact, Phildaelphia’s 66-run differential, compared with the Yankees’ 115, shows the difference between the two teams’ scoring habits. The Phillies have the luxury of relying on low run production (they’ve produced about 78% of the Yankees’ production) due to their fantastic pitching. On the other hand, the Yankees are struggling with a 3.53 starters’ ERA including Ivan Nova and AJ Burnett, both over 4.00, as full-time starters. The Phillies have three pitchers with 17 starts and an ERA under 3.00 (Halladay, Cliff Lee, and Cole Hamels) and Joe Blanton, who has an ERA of 5.50, has only started 6 games. Even with Blanton bloating it, the Phillies’ starer ERA is only 2.88.

That doesn’t, though, make the Yankees a badly-managed team. In fact, there’s an argument that the Yankees are MORE efficient because they’re leading their league, just as the Phillies are, with a much worse starting rotation, through constructing a team that can balance itself out.

That’s the problem with wins above expectation – they lend themselves to multiple interpretations that all seem equally valid.

Tables are behind the cut.

\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|}  \hline  Tm&W&L&W-L \%&RS&RA&pyth \%&pythW&WAE&rDiff&Alpha\\\hline  NYY&48&31&0.608&421&306&0.640&50.60&-2.60&115&-0.033\\ \hline  BOS&46&34&0.575&415&333&0.598&47.87&-1.87&82&-0.023\\ \hline  TBR&45&36&0.556&341&312&0.540&43.75&1.25&29&0.015\\ \hline  DET&44&38&0.537&378&370&0.510&41.79&2.21&8&0.027\\ \hline  CLE&42&37&0.532&340&330&0.514&40.57&1.43&10&0.018\\ \hline  TEX&43&39&0.524&380&362&0.522&42.80&0.20&18&0.002\\ \hline  LAA&42&40&0.512&313&308&0.507&41.60&0.40&5&0.005\\ \hline  TOR&40&42&0.488&368&367&0.501&41.10&-1.10&1&-0.013\\ \hline  CHW&40&42&0.488&335&340&0.493&40.45&-0.45&-5&-0.005\\ \hline  SEA&39&42&0.481&277&290&0.479&38.82&0.18&-13&0.002\\ \hline  BAL&35&43&0.449&322&379&0.427&33.29&1.71&-57&0.022\\ \hline  OAK&36&46&0.439&282&300&0.472&38.71&-2.71&-18&-0.033\\ \hline  MIN&34&45&0.430&287&369&0.388&30.67&3.33&-82&0.042\\ \hline  KCR&33&48&0.407&348&397&0.441&35.69&-2.69&-49&-0.033\\ \hline \hline  Tm&W&L&W-L \%&RS&RA&pyth \%&pythW&WAE&rDiff&Alpha\\\hline  PHI&51&31&0.622&329&263&0.600&49.20&1.80&66&0.022\\ \hline  ATL&47&35&0.573&321&277&0.566&46.44&0.56&44&0.007\\ \hline  SFG&46&36&0.561&287&286&0.502&41.13&4.87&1&0.059\\ \hline  STL&44&38&0.537&389&362&0.533&43.67&0.33&27&0.004\\ \hline  MIL&44&38&0.537&355&346&0.512&41.95&2.05&9&0.025\\ \hline  ARI&44&38&0.537&371&363&0.510&41.81&2.19&8&0.027\\ \hline  CIN&42&40&0.512&395&354&0.549&45.05&-3.05&41&-0.037\\ \hline  PIT&41&39&0.513&304&312&0.488&39.06&1.94&-8&0.024\\ \hline  NYM&41&40&0.506&369&356&0.516&41.81&-0.81&13&-0.010\\ \hline  WSN&40&41&0.494&314&310&0.506&40.97&-0.97&4&-0.012\\ \hline  COL&39&42&0.481&356&356&0.500&40.50&-1.50&0&-0.019\\ \hline  SDP&37&45&0.451&285&309&0.463&38.01&-1.01&-24&-0.012\\ \hline  FLA&36&45&0.444&301&343&0.441&35.73&0.27&-42&0.003\\ \hline  LAD&36&46&0.439&316&346&0.459&37.64&-1.64&-30&-0.020\\ \hline  CHC&34&48&0.415&337&410&0.412&33.80&0.20&-73&0.002\\ \hline  HOU&29&53&0.354&328&411&0.399&32.74&-3.74&-83&-0.046\\ \hline  \end{tabular}

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