the 2015 Nationals summary I'm keeping up to date for details, but while SoCal has won only one Nationals Championship, they have made the semi-finals in 7 of the other 9 events including 3 second place finishes.
Last year, the sections that did well at Nationals found themselves with a far larger number of players bumped up than bumped down as part of the year-end calculations and also what appears to have been some manual adjustments the USTA made to try to make the sections more even. What is interesting is that SoCal was one of the sections that did receive more bumps up than average and they seem to be doing even better than last year so far.
Perhaps there is just a larger pool of players in SoCal, or they've been able to draw new players in to league play that have increased the pool of good players, but in any case at least in the 18 & over division, SoCal has dominated. Using the points I assign for results, SoCal has 21 and the next closest, Florida, is at just 12. With a strong finish next week in the 2.5 division, SoCal could double the next closest pursuer.
Does this mean SoCal will see another adjustment at year-end to bump more players up? We'll see in about 7 weeks when year-end ratings come out!