Two adjacent CBSAs will merge to form one CBSA if the central county or counties (as a group) of one CBSA qualify as outlying to the central county or counties (as a group) of the other CBSA using the measures and thresholds stated in 3(a) and 3(b) above.
[CBSA is the umbrella term for MSAs and µSAs]
3(a) and 3(b) are:
A county qualifies as an outlying county of a CBSA if it meets the following commuting requirements: (a) At least 25 percent of the workers living in the county work in the central county or counties of the CBSA; or (b) At least 25 percent of the employment in the county is accounted for by workers who reside in the central county or counties of the CBSA.
So it sounds like if 25% of San Francisco County residents work in Santa Clara County, or 25% of SF jobs are taken by Santa Clara County residents, they would merge the two MSAs. Presumably this is not the case, and thus the MSAs are separate.
The Census does have a higher-order concept called a "Combined Statistical Area". The whole Bay Area is lumped into one CSA: http://en.wikipedia.org/wiki/San_Jose-San_Francisco-Oakland,....
http://en.wikipedia.org/wiki/List_of_Metropolitan_Statistica...
The wiki page suggests that these are based on social and employment connections that are inferred in part from commute patterns.
Perhaps the pairing of SF and San Mateo reflects growing social and economic links between the Peninsula and SF in a way that eclipses SF and San Mateo's historical affinities with Oakland and San Jose respectively.
I find Greeley particularly surprising. It's mostly known for the afternoon smell due to the stockyards (cattle) in town. My best guess is it's due to the fracking-powered oil boom in the area.
Agreed. How is it a "large" city ?
While national articles like this are quick to attribute Fargo-Moorhead's success to energy, I'm a little more skeptical. The region's economy was seeing good growth even before the oil boom, mostly driven by a strong agriculture economy and lots of higher education. Oil has no doubt been a bit of a catalyst, but I think the region would be seeing prosperity even without it.