The first analysis comes from FightMatrix.com, which gives numerical rankings to fighters sort of like the BCS college football computer rankings.
Here's how FightMatrix.com describes its division dominance list:
This list ranks fighters based on their point level superiority over those in the division in which they are currently ranked.The FightMatrix.com rankings put St. Pierre first, with a pretty sizable gap between him and No. 2 Anderson Silva and No. 3 Fedor Emelianenko, who are virtually tied. I think most fans would look at the FightMatrix.com rankings and say they're generally pretty credible, and GSP's presence at the very top says a lot about how he's dominated his weight class.
This is done by averaging the point level which encompasses the typical transition between the elites and top contenders of the division, then compares this average to the fighter's current point level. The higher a fighter's division dominance points, the more "dominant" they are over their divisional peers.
The second analysis comes from BloodyElbow.com's FightLines, which provide one big chart showing who's beaten who in the welterweight division.
It's really amazing to look at that chart and see how vast the welterweight division is, and how dominant St. Pierre is over it. It's especially amazing when you consider that St. Pierre absolutely dominated both Jon Fitch and Thiago Alves, who themselves have completely dominated the welterweight division when they're not fighting St. Pierre or each other.
Fitch has won 11 of his last 12 fights and the only loss was to St. Pierre. Alves has won nine of his last 11 fights and the only losses were to Fitch and St. Pierre. Just about every top-notch welterweight has lost to either Fitch or Alves (who will fight each other at UFC 111), but neither one of them was even competitive against GSP.
Anyway, consider this food for thought as we prepare to watch St. Pierre take on Hardy in two weeks. If St. Pierre wins, he'll have cleaned out the welterweight division to such an extent that there's not much left for him to do. Except maybe move to middleweight.