THE BOOK--Playing The Percentages In Baseball

Looks like the academic work agrees what I have done previously:

http://www.beyondtheboxscore.com/2010/4/1/1399848/comparison-of-hitters-and-pitchers

Another note on the injuries before the All-Star, about 10% of DL trips happening the first day of the season with others trickling in.

I think Neyer nails the explanation for the “75% of injuries come before the all-star break”—selection bias.  Don’t know if the academic authors touched on any of Neyer’s points in their paper.

Number of DL trips, all players, 2002-09, by month:

1 0
2 0
3 419
4 784
5 634
6 562
7 490
8 531
9 93
10 1
11 0
12 0

So, yeah, you have a definite bias in DL assignments.  July has about 10-15% fewer games (because of the All-Star game), and so, it’s no surprise that DL assignments in July is about 10-15% less than June and August.

The average of March/April is 600, and that’s in-line with May/June.

All-in-all, nothing there.

#3 - What exactly are getting at with:

The average of March/April is 600, and that’s in-line with May/June.

The number of regular seasons games in March is usually very minimal.

Jeff/4, if teams tend to delay moving players to the DL for injuries recorded during spring training until the season starts, DL trips for injuries that occurred during March may be recorded during April.  That would explain why April has a higher total than any other month.

Regular season games don’t occur in March very often, but spring training games do, and it’s probably a decent starting assumption that injury rates in spring training games are similar to injury rates in regular season games.

Mike said exactly what I wanted to say in fewer words and more clarity.

I main problem is that some of these players were injured/had surgery way before March, like Carlos Beltran.  He wasn’t hurt during ST or because of it.  There are quite a significant number of players that had off season surgeries in Sept and have to wait into the season to come off the DL. 

Also, players don’t play as long or as hard in ST games, so the rate of injuries should be less.  I have to go back through the injuries to which are caused before or during ST.  I am busy for a few days (watching 5 kids under 7 by myself), but should be able to get the numbers within the week.  Someone hit me up if I don’t have anything by Monday.

From the work I have done, there seem to be less injuries in the first part of the season. 

Just thinking out loud:  One way may be to compare all players on DL from one season to the next.

Best bet is to look at things on a weekly basis, starting from the 2nd week of April.  Before then, you have shenanigans that could cause inaccurate results.  Reported DL dates is not the same thing as date of injury.

I have finally gone back and divided the data bi-monthly and taking out the first couple of weeks of the season, the data seems fairly constant.  The only trend I might see in the DL rate for pitchers may go down as the season goes on:

Date Starting Total Trips Number of Days Average Per Day

Pitchers
Before 4/15 380 Before 4/15
04-16 146 15 1.39
05-01 159 15 1.51
05-16 133 16 1.19
06-01 148 15 1.41
06-16 135 15 1.29
07-01 105 12 1.25
07-16 107 16 0.96
08-01 119 15 1.13
08-16 146 16 1.3
09-01 35 15

Batters
Before 4/15 266 Before 4/15
04-16 103 15 0.98
05-01 132 15 1.26
05-16 163 16 1.46
06-01 127 15 1.21
06-16 116 15 1.1
07-01 109 12 1.3
07-16 111 16 0.99
08-01 135 15 1.29
08-16 102 16 0.91
09-01 36 eos

Combined
Before 4/15 646 Before 4/15
04-16 249 15 2.37
05-01 291 15 2.77
05-16 296 16 2.64
06-01 275 15 2.62
06-16 251 15 2.39
07-01 214 12 2.55
07-16 218 16 1.95
08-01 254 15 2.42
08-16 248 16 2.21
09-01 71 eos