The defensive spectrum, however, particularly the notion that middle infielders and catchers are not expected to hit as much as other players, has not been entirely constant over time. The basic framework has applied for over a century, but the extent to which it has been accurate has varied. At first glance it would seem like currently there are more middle infielders who contribute offensively, and fewer who are in the lineups exclusively for their gloves, than a generation ago, but this alone does not represent strong evidence.