ZappCatt's breakdown looks pretty accurate for a typical southern California race. Usually there will also be a 40+ or a 45+ and sometimes a 50+ or 55+ race also. 30+ races are really not that popular in southern California. They are offered but not as often as the other masters categories. Since masters racers can go down in category ( a 42 year old can race the 40+ race and the 35+ race) it is not uncommon to see many masters double up. I have seen Thurlow Rogers win a 40+ race, place top 3 in a 35+ race and then be top 5 in the Pro/1-2 race in one day.