[Racer26]

The number of open registration slots shrinks every year because of more and more regionals starting.

The growth rate is also non-linear.

In 2003, when I was a rookie, 1114 was one of the highest numbered teams.
In 2007, 2056 was one of the rookies
In 2011, we had 3739 as a rookie.

The rate of team growth roughly doubled from 2003-2007 to 2007-2011, and it continues to accelerate.