Home Runs and Runs Scored per Game

The number of home runs per game and runs scored per game are perhaps the two trends that reveal the most information about bat performance in the field. When players are swinging hotter bats, they will more frequently hit the ball out of the park for a home run and teams will tend to score more runs during a game. Furthermore, the proliferation of home runs and runs scored was the primary reason that performance standards were first implemented in 1999 and significantly modified in 2011.

The two plots in this section show the number of home runs per game (top plot) and the total number of runs scored per game (bottom plot) for NCAA Division I college baseball from 1970 through 2014. Both data sets indicate that immediately after aluminum bats were introduced in 1974, a greater percentage of hit balls began going over the fence and more runs were being scored each game. There is a steady increase after aluminum bats were introduced until 1986 when weight limits were imposed. I don't know exactly what happened in the early 1980's to produce the surge in home runs, but 1985 was the year the very popular Easton Black Magic baseball bat was introduced.[8] The drop in home runs and runs scored after 1985 may be due to the fact that the NCAA introduced the "minus 5" rule after that year. This rule stated that the numerical difference between the bat weight (in ounces) and the weight (in inches) could not be more than 5 units. A 34-inch bat manufactured in 1986 could weigh no less than 29 ounces. This change would have had an effect on bat swing speeds and might partly explain the immediate drop in batting averages starting in 1986.

But, bat performance didn't stay down for long. Starting in 1996 batting averages began increasing at a dramatic rate, reaching an record high during the 1998 season. The NCAA Baseball Rules Committee had convened a "bat summit" in 1994 and bat manufacturers agreed use the Brandt BPF test (designed to measure the performance of softball bats) to measure baseball bat performance with a "gentleman's agreement" not to produce bats hotter than those used in 1994. However, as the data clearly shows, bat performance increased sharply during 1996-1998, even though manufacturers claimed their bats were passing the Brandt test. The 1998 College World Series saw a record number of NCAA records broken, * and the number of home run and runs scored per game reached an all-time high. Alarmed by this drastic increase in performance, the NCAA implemented a bat performance standard for the 1999 season. Effective in August 1999, the NCAA adopted BESR performance standard, along with the "minus-3" rule for bat length and weight, introduced a lower limit on a bat's moment-of-inertia, and a reduction in the maximum allowed barrel diameter. Once bat performance was being controlled through laboratory testing and certification processes, bat performance quickly dropped, and from 2003-2007, bat performance returned to levels seen between 1978-1982 and 1989-1995.

During the 2008-2009 seasons the number of home runs and runs scored per game once again began increasing, mostly likely due to the increasing popularity of composite bats. During the 2008 season the NCAA became aware of the fact (well known in the slow-pitch softball world for several years) that the performance of composite bats improves as the bats are broken in through use. This would explain the increase in batting averages and home runs, even as the pitching appears to be improving (data below shows strike outs per game increased a the same time). After conducting several tests during the 2009 College World Series, the NCAA discovered that the majority of composite bats in play exceeded the BESR performance standard after been sufficiently used (even though those same bats had passed the standard when brand new). In July of 2009, the NCAA passed an immediate and indefinite moratorium banning composite bats.[3]

At the same time the NCAA was deliberating over what to do with composite bats, they were also considering a significant change in their bat performance standard. In October 2008, the NCAA announced plans to abandon the BESR performance standard standard for a new BBCOR standard, effective January 1, 2011.[4] This change was implemented after extensive testing confirmed the scientific prediction that non-wood bats which passed the BESR + MOI performance standard could indeed hit balls up to 5-6 mph faster than a high performance wood bat. The new BBCOR requires that all bats must produce a bat-ball-coefficient-of-restitution that equals 0.50 or less - which is the maximum value for a wood bat. From the data I have seen, this means that about 70% of the BESR-approved bats available for play during the 2009-2010 season are no longer legal for play today.

The effects of the BBCOR=0.50 standard are very obvious. As I had expected, the NCAA adoption of the BBCOR=0.50 bat standard in 2011 has caused the number of home runs and runs scored per game to drop almost to pre-aluminum values (the lowest number of home runs per game since 1974). This is very significant. After the BBCOR=0.50 standard was adopted, batters were not hitting home runs with anywhere near the frequency that they had during the last 30 years.

In 2015 NCAA switched to a flat-seam baseball, in an attempt to recover some of the offense and run production that had been lost with the adoption of the BBCOR bat standard. The flat-seam ball is rounder and smoother, resulting in less air-drag so that it travels farther when hit. Indeed the number of homeruns per game and the number of runs scored per game are quickly increasing since the 2015 season due to the farther carry of the flat-seam ball.