The NBA  is getting bigger by the year.

Interesting reading from Business Insider:

CHART OF THE DAY: The Strange History Of Height In The NBA

Sometimes when you hear guys like Bill Walton waxing poetic about the NBA, one of the common themes is that there are not very many "true centers" left. You know, the back-to-the-basket, 15-rebounds-a-night bruisers. So with a guy like Shaquille O'Neal on his last legs, it left me wondering if the number of 7-footers in the NBA has changed in recent years.
In a word, no. As we can see below, the number of 7-footers in the NBA has remained relatively unchanged over the last 18-20 years.