Another interesting trend over the last few decades has been score convergence across clusters at the 90th percentile. Thus, scores have not only converged within schools as the range from the 10th to the 90th has fallen, but scores have also converged across schools. This is probably a result of the ceiling effect in that there is little room for the 90th percentile of the ultra elite schools to increase.
It should come as little surprise that many of the elite schools caught up with the 90th percentile of the ultraelites. For example, Duke's 90th was more than 100 points behind Columbia's 90th in the early 1980s but in the early 2000s the 90th percentile values of the two schools were the same. Likewise, UCLA and UC Berkeley had a 90th some 50 points below that of Chicago GSB in the early 1980s. Some two decades later, the 90th percentile at the three schools was essentially the same.
What is more interesting is that schools from lower clusters have come very close to the 90th percentile of the ultraelites. For instance, in the early 1980s the 90th percentile of Columbia was near 700. This was some 80 points above the 90th at Emory. Two decades later, Columbia's "lead" had diminished to only about 30 points.
A similar pattern can be observed with the elite schools as well. In the early 80s Cornell had a large lead of about 60 points on its fellow NY school Rochester. Two decades later, this lead had fallen to just 10 points.