[LA21st]

For whatever reason, they don't count the Riverside and San Bernardino counties ,which would make it 18 million or so for LA.
Not sure why, they're basically extensions of LA County and Orange County. Much of SB shares the freakin' LA county street grid.

The Inland Empire is the "affordable" region of the LA area. The Inland Empire associates with LA. There wouldn't be 4 million people there without Orange and LA county nearby.

As far as CSA goes, LA can surpass NYC metro in our lifetimes, barring natural disasters. It's a lot more realistic than DFW or Houston passing LA, that's for sure.