Saturday, July 5, 2014

Finding the Best Division in Baseball using BaseRuns

The best division in baseball is a title that is hotly disputed among baseball fans.  Oftentimes sportswriters claim the superiority of one division over another, however they rarely use empirical evidence to back up their claims, instead relying solely on anecdotal evidence.

There is, however, a way to find the best and worst divisions in an objective manner.  FanGraphs recently started publishing Team BaseRuns, a team statistic that gives a team's expected run differential and win percentage based on its underlying offense, defense, pitching, and base-running.  If you want to find more about BaseRuns, this article by Dave Cameron does a good job at explaining the basic methodology behind the method.  The system is also validated by recent research.

Now that we are familiar with BaseRuns, let's sort each division by expected win percentage:

AL East

Blue Jays - .530
Orioles - .513
Rays - .497
Yankees - .465
Red Sox - .441

AL Central

Tigers - .563
White Sox - .485
Indians - .481
Royals - .474
Twins - .463

AL West

A's - .626
Angels - .605
Mariners - .537
Astros - .458
Rangers - .380

NL East

Nationals - .565
Braves - .515
Marlins - .477
Mets - .475
Phillies - .434

NL Central

Cardinals - .555
Pirates - .522
Brewers - .513
Reds - .511
Cubs - .501

NL West

Dodgers - .576
Giants - .528
Rockies - .476
Diamondbacks - .426
Padres - .418

Next, let's sort the divisions by average winning percentage to find out the divisional strengths.  

  1. AL West - .521
  2. NL Central - .520
  3. AL Central - .493
  4. NL East - .493
  5. AL East - .489
  6. NL West - .485
This list is a good starting point, but unfortunately it doesn't paint the full picture.  The American League has been the stronger league for quite some time, and still is in 2014.  This is the AL's record against the National League, in both 2013 and 2014, as provided by Vegas Insider and Wikipedia:  (I include data from 2013 because the 2014 season is not yet complete.  Also I weight the two seasons equally (even though 2013 has twice as much data) because 2014 data is more relevant.)

2013: 154-146 - .513 
2014: 90-81 - .526

Averaging the two winning percentages, we can see that the AL going forward can be expected to have a .520 winning percentage against the NL, while the NL can be expected to have a .480 winning percentage against the AL.  By dividing these winning percentages by .500, we get a multiplying factor for each league. 

AL: .520/.500 = 1.04
NL: .480/.500 = 0.96

After multiplying each divisional average BaseRuns winning percentage by the League Multiplying Factor, this is what we find:

  1. AL West - .542
  2. AL Central - .513
  3. AL East - .509
  4. NL Central - .499
  5. NL East - .473
  6. NL West - .466
Clearly, the AL West is far and away the best division in baseball, despite being home to two of the worst teams in baseball, the Rangers and the Astros, because of the A's and the Angels, baseball's two best teams playing in baseball's best league.  

In addition, baseball's best division got even better yesterday with a blockbuster trade between the A's and the Cubs, sending talented pitchers Jeff Samardzija and Jason Hammel to Oakland for prospects.  

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