Air Density and totals in baseball?

I don’t know how many times I’ve looked at the total for a Rockies game and thought there’s no way they score 11 runs today. Especially in the day and age where pitching dominates baseball and you’ll regularly see totals in the 6 and 6.5 range.  So I’ll often stay away from betting the total. Traveling to Denver for work about every month for the last four years I watch my fair share of Rockies games on TV and at beautiful Coors Field. The running theme on sports talk in Denver is that the Rockies can never find pitching and always have plenty of bats. So after watching BP at Coors a couple weeks ago and seeing about every other ball fly over my head (sitting in left field about 15 rows up) my inner gambler got to thinking, how often do totals go over at Coors?

So I got to work, the primary metric I looked at was Air Density Index.  Simply put a lower air density index and the ball will travel further with less resistance. The air density index at Coors (higher elevation, thin air) is far less than that of a team at sea level.  Coors field has an Air Density Index that will typically be in the mid to high 50s (depending on day/month) while a game at Fenway will typically be in the low to mid 70s.

My first step was to look at totals at Coors field. I gathered data for the last 30 games played at Coors every month over the last 3 years and change (the change includes April 2016). The total really surprised me as the total has gone over at an astonishing rate

99 – 75 – 6 (56.9%)

I then gathered the same data for a few other teams that typically have a lower air density index. On average less than 65.

DBacks: 91 – 81 – 8

Royals81 – 93 – 5

Rangers: 79 – 88 – 9

Braves: 83 – 80 – 17

Astros: 81 – 93 – 5

This number was also a bit eye popping as these five teams had a combined 412-436-47 where the over hit at a 48% rate. The interesting thing is the DBacks who play in a re-tractable roof (where the Air Density Index can vary mind you). Average the lowest air density index of the the rest of the teams (aside from the Rockies of course). So if you strictly bet the over in a Rockies and DBacks home game your record would be 190-156-14 (55%).

I must admit the gambler in me wanted to find an edge between teams that average an air density index less than 65 and the rest of the field. But realistically that just didn’t happen. I fortunately did have an edge that I will pursue in the future with totals at Coors and Chase Field.


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