You tease! <img src="http://www.catsailor.com/forums/images/graemlins/laugh.gif" alt="" />

I (still) believe it is down to the skill of the sailors, and time in the boat builds skill. You build skills faster if you use the time spent on the boat to train seriouosly instead of zipping around.
This summer I had the opportunity to talk with the skipper of the norwegian tornado in the '84 L.A 'games. He said that they had bin finishing in the middle of the pack for some years, until the spent a winter sailing the boat instead of putting it in storage. Then they jumped up to be a top ten finisher consistently. Time in the boat made all the difference for them. Same time at Kielerwoche the russian team came with some old worn out beater sails, but was still the fastest boat on the water due to time in the boat.

But from time to time there is a technical improvement, like the Gran Segel spis who blitzed the fleet at the Tornado worlds in Marthas Vineyard '02. Now everybody has moved to the same shape, or even more extreme variations of the same shape.