Originally Posted by Pony Boy
And the use of closers in the 80s, 90s and 2000s also coincides with a huge increase in offense league-wide (smaller ballparks, expansion/watered down pitching, and PEDs). More offense means a greater chance for blown leads.
I would make the case that pitcher specialization (use of lefty vs. lefty and righty vs. righty more often) had a much bigger impact than the use of a bullpen's best pitcher only in the 9th inning in certain situations.
Plus overall runs for the last 3 years on a per game basis is very similar to the mid to late 70's. Perhaps the 2010's vs. the mid to late 70's would be a nice comparison.