The data for Infield Out Prevention goes back to 1988, but it is only reliable as far back as 2003, so that is all that’s included in the table below. Data is for all of MLB; links go to Baseball-Reference.

Major League Average IFOP and IFO/C by Year

UPDATED 10/30/11: IFOP went way up in 2011, and IFO/C continued its downward trend for the 5th straight year. There were more balls hit on the infield in 2011 than in any year since 2005, and the most infield hits and fewest double plays on record. Clearly, there’s been a shift since 2005-6 toward speedier players and away from huge sluggers.

As you can see, 2010 was a pretty good year for preventing infield outs, at least relative to recent years. I suspect that the late 90′s and early “aughts” were the worst years for IFOP, though the data before 2003 is so sketchy it’s hard to say for sure. In the past couple years, teams have begun to place a greater emphasis on speed, which no doubt is the reason for the slight uptick in IFOP.