In 1988 the VMG (velocity on course) of the AC winner was 11.3 and 8.3 (knots, apparently, according to wikipedia) in two races.
By in 2010, this figure had come up to 15.7 and 18.5 (knots, same source).
(Not sure what speeds were between 1988 and 2010.)
For this AC, we are now looking at an average of twenty - what??
This is not apples to apples, longer courses, less wind, very different boats, but this increase seems proportionally more than other sailing races, say, Vendee Globe times?