Position-by-position tiers: Catchers; First basemen
Teams have very gradually asked more offensively from second basemen over the decades, a slow-moving trend that dates back to the 1950s. Lately, though, you have to wonder if that's the only thing that's changing at the position.
One undeniable trend is that second basemen hit for more power than they used to. According to positional data from Baseball Prospectus, dating back to 1951, this been an up-and-down proposition over the years, but it has settled in at the upper end of the roller coaster.
In 1951, those who played most of their games at second base accounted for 7.