Strikeouts

I recently picked up this 1961 Topps NL Strikeout Leader card:

 I picked it up for my Giants collection as it features Sam Jones in 3rd place in the NL with 190 strikeouts.  Obviously the two starts of the card are the Dodgers Duo of Koufax and Drysdale.  Drysdale beat out the competition by almost 50 strikeouts, very impressive.

I really enjoy the back of this card showing the leaders all the way back to the turn of the century.  When I started looking at this more closely I found it something that stood out as somewhat odd to me.  Take a look at the total for the league leaders prior to 1958. There are only 16 total seasons of 200 or more strikeouts by the league leader.  In the stretch from 1929 to 1957 there are only 2 seasons where the leader was over 200 Ks.  Now, starting in 1958 we have 3 straight years.

I started to think through my baseball history knowledge to see if I could recall anything that could have made the strikeout become more prevalent.  First I thought, maybe it is just Don Drysdale, 2 of the 3 years were his seasons, maybe he was starting on a streak like Christy Mathewson in the early 1900s.  We all know that 200 Ks is fairly common now so it couldn't just be Don.  Maybe it was the expansion of the schedule, I recall that sometimes in the late 50s or early 60s baseball went to to the 162 game schedule from 154. I thought that would be about 2, maybe 3 starts, I guess that could push some of the 180s and 190s into the 200 range but then I looked it up and the change didn't take place until 1962 in the NL so the change had already started.

Thinking of how many starts that extra 8 games would equate to for a starter reminded me that in this era, most rotations were only 4 deep and now they are 5.  That coupled with more relievers in today's game should reduce innings counts and therefore strikeout totals.  I decided to look at the K totals for the league leaders in the NL since 1960. Here they are:

 Only 2 seasons since 1957 has the league leader been under 200, 1981 when Fernando had 180 in the strike shortened season and 1994 when Andy Benes has 189, again a strike shortened season.  Pretty easy to assume both would have gotten over the 200 mark if the strikes had not intervened. 

For some reason, strikeouts started to increase in the late 50s and continue at a high level today. I haven't been able to find any explanation other than just evolution of the game.  Anyone out there have any ideas of what has driven the increase in strikeouts?  Rule changes?  Pitching training?  Approach to the game?  More power hitters?  If you have any insight that could help put the wheels that are cranking in my head to rest on the subject, I would be interested to hear your theories.