How about addressing some world records that have not been broken in a greater length of time, such as:
Discus - 7,668 days
Hammer - 7,583 days
Shot Put - 6,224 days
Pole Vault - 4,690 days
High Jump - 5,059 days
Long Jump - 5,756 days
Javelin - 4,027 days
All of these were set between 1986 & 1994. Where have all the greats gone?
Two words: Cold War. The Cold War prompted not only an arms race and a space race but an athletics-prowess race between the Soviet Union, the U.S. and their respective allies. East Germany was the front line in the war of athletics-superiority. With a huge government-subsidized athletics program that accelerated steroid research, East German athletes did remarkably well on the world athletics stage, especially at the 1976 and 1980 Olympics. Government officials, physicians, researchers, coaches, trainers – along with virtually every East German elite athlete – all conspired to create the world's most advanced steroids program, and did so in the name of Communism. With the fall of the Berlin Wall, East Germany – along with its steroid program – ceased to exist. With the end of the Cold War came the end of the need for all those monstrous athletes on both sides of the Iron Curtain, along with all those monstrous jumps and throws. Drug use continued, and continues to this day, but certainly not for the ideological reasons which prompted the huge increases in doping during the Cold War. Beginning in the 90s, better drug-testing methods put a stop to virtually all of the records in events that require power.
But time marches on, and so does the progression of humans in athletic performance. If we could somehow wipe out the late 60s through the early 90s from the annals of track and field history, we'd find that the progressions for the field events are now continuing at roughly the same rate they did before that 25-year period began. Unfortunately, the record books are still radioactive due to all of the fallout from the Cold War. Even more tragically, the former Soviet-Block athletes are the ones who are now suffering the most.