Here's a quick and dirty look (we will let you decide which is the more prominent of these descriptors on your own...) at the distribution of offensive achievement by age, in the form of yet another of our handy (not-so-handy?) charts.
In case you skipped the title, the measure here is adjusted OPS (OPS+). These are broken down by ages (20-40), then slammed together into four age ranges (-25, 26-29, 30-34, 35+). These are the hitters who currently qualify for the batting title.
What does it tell us? That top-level hitting (150 OPS+ or higher) is strongly correlated in 2013 toward younger hitters, but that teams often carry below-average young hitters (see ages 23-25) either in hopes that they will improve or because they are playing positions at the left edge of the defensive spectrum.
The summary chart shows this a bit more directly. Young hitters are far more likely to be below-average in OPS+ (at least in 2013; we're gonna go back and look at this for past years soon...); players in Age Range 3 (30-34) seem to be around mostly because they can still hit.
Most of these occur in the age 30-32 range, however: when we break out the Age 3 data by 30-32, 33-34, we get 39-17 for the first group, 11-6 for the second group. Even with the selection bias, older hitters (who are still around at age 33-34 because they are supposed to be able to hit, or may have done so in the earlier portions of Age Range 3) are declining relative to league average (70% above the line for age 30-32, 64% for age 33-34).
More on this a bit later....