From More On The Changing Historical Relationship Between Walks, HBPs and HRs
-There is a significant positive relationship between a pitcher's walk rate and his HBP rate
-In the 1960s, a pitcher who gave up more HRs hit fewer batters but today a pitcher who gives up more HRs hits more batters.
From The Changing Historical Relationship Between Walks, HBPs and HRs
-For both leagues, the HBP/Walk rate has been rising since 1980 (so poor control is not the only reason for more HBP).
-In recent years (up through 2007), the HBP/HR rate has been relatively high, even adjusting HBPs for control as measured by the walk rate.
From Do Sluggers Get Hit By The Pitch More Than They Used To?
-players who hit HRs more frequently are now more likely to get hit by a pitch than in the the 50s, 60s and 70s.
-hitting a HR in the 1990s was 83% more dangerous in the 1990s than it was in the 1960s in terms of causing the player to be HBP.