RadioPhillyFan said:
With all that taken into account,
How is the nations forth largest city and metro AND city, surpassed by a city with less then a half million people?
Look at the TV DMA's... Nielsen's version of metros. When TV markets were extended via Community Antenna TV services... now just called "cable" we saw the Salt Lake City market include big pieces of Montana and Wyoming, too.
Arbitron originally create the Metropolitan Survey Area based on a set of criteria that started with a home county and then added surrounding counties to the extent that a certain percentage of listening was to the home county stations and a certain percentage of commuting was towards other parts of the metro.
Of course, even if a bunch of stations have signals farther out, when there is a big adjacent market, with more listening to its stations, that county falls to the "other" market. Think Baltimore vs. DC. or Hartford vs. Springfield or Dayton vs. Cincinnati.
Once markets are established, there is the possibility of adding or consolidating metros... in 1980, the Ft Lauderdale and the Miami metros were combined into one MSA... but only after all local subscribers had voted (I was there as GM of WHTT-1260 in Miami).
In the majority of cases, although far from all of them, the Census / OMB definition of a Metropolitan Statistical Area matches the Arbitron Metropolitan Survey Area. That is because many trade areas are wheel and spoke in nature... with commerce and population revolving around the central city area and the larger AM and most C or B FMs covering the area, thus making the Census and Arbitron areas match.
When a county no longer qualifies, it may be dropped... Arbitron redefines counties in MSAs annually and issues a list of changes.