This report looks at league hitter and pitcher trends since 2005. Please note that older data covers scouted plate appearances; Inside Edge charted 91 percent of league PA in 2005 and 93 percent in 2006. Inside Edge charted 100 percent of PA beginning with 2007. Data for 2012 covers games through June 11. All data are for hitters batting (excludes pitchers batting).
Batting averages have remained fairly consistent on counts before two strikes, although with a general trend of less contact. In play per swing percentage (right-hand column) is the ratio of balls put into play per swing.
With the count at two strikes, pitchers have become increasingly dominant with higher swing-and-miss percentages, more two-strike counts resulting in strikeouts, and weaker contact when the ball is put into play. Well-hit average in play is the ratio of well-struck balls to all balls put in play.
Hitter performance has declined when runners are in scoring position. The trend is towards fewer quality at-bats in this situation. Quality at-bats include hits, well-hit outs, 7-pitch or more outs, walks, HBP, sac bunts and sac flies. Once again the trend is more misses, less contact, and fewer hard-hit balls.
Starting pitchers and relievers share the same trend of getting more swing-and-misses and weaker contact.
Among hitters, the greatest declines in production are with players whose usual defensive positions are third base and second base. This might suggest a move among teams of favoring defense over offense at these two positions in the middle of the traditional defensive spectrum.
Improved fielding could be responsible for some of the offensive decline. This trend is not as clear as some of the others, but batting average on ground balls has generally decreased in recent years.
Conversely, batting averages on well-hit balls are trending in the opposite direction. Besides dampening the idea that improved defense deserves too much credit for weaker offense, the trend may also suggest that sluggers are doing as well as ever – they deliver when they hit the ball hard – but that there are fewer hitters in the league capable of making consistently hard contact.
Turning to pitching trends, fastballs are generally being thrown less often but with higher miss percentages. Fastball velocity has steadily increased; it is unknown whether that is a measurement artifact, although the miss percentages suggest it's real.
With fewer fastballs, usage of the high miss percentage curve is on the upswing.
Inside Edge has charted pitch subtypes (e.g. 2/4 seam fastballs) for only a few years, preventing comparison to historical pitch repertoire tendencies. In 2011, 40.2 percent of pitchers threw at least three distinct pitches while just 27.5 percent regularly used only one or two types. Anecdotal evidence suggests larger repertoires have grown more prevalent. Our previous research found a positive relationship between pitcher performance and throwing a bigger variety of pitch types, provided the additional pitches are of at least league average quality.
The cut fastball is a subtype that is getting increased usage. Cutters were thrown 2.8 percent of the time in 2009. The percentage was 3.2 percent in 2010-11, and it has risen to 3.8 percent so far in 2012.
One other item: The percentage of taken strikes has increased slightly, from 27.1 percent in 2005-08 to 28.0 percent in 2009-12. It's a small effect, but indicative of hitters being slightly less aggressive against pitches in the strike zone.