Im just not sure how NBC and CBS got the evidence that San Francisco is a larger Media Market than Los Angeles came from but I seen the 1930's census showing Los Angeles is larger than San Francisco at that point though. In the case of KCBS going to San Francisco wasn't this issue a debate over who got the CBS affiliation on 740 AM. Because KSFO was mentioned as one of the CBS Affiliates in the Bay area at the time and KQW was moving from San Jose to San Francisco at that time though.
Radio stations and media in general don't look at the population of individual cities... they look at metropolitan areas.
Up until the 1930 Census, San Francisco's metro was bigger than that of Los Angeles.
I already posted this link that shows metro area populations by decade, but here it is again:
http://www.city-data.com/forum/city-...as-decade.html
LA became important to radio with the growth of "talking" motion pictures, since many performers were featured in both radio and movies. This became significant, and despite San Francisco being the larger financial and communication center, it swung radio's interest in LA's favor even during the difficult years of the Great Depression.