Within a metropolitan area, all sub-markets are “connected”.
The “bi-and trifurcating” that you observed is only a temporary phenomena. Any competent RE appraiser will tell you this.
There is a large number of newly built homes in Contra Costa county & Solano county. When prices go down in Contra Costa county & Solano county, that’s bad news for the rest of the bay area. As prices collapse in the east bay, it will draw buyers from the rest of the bay area.
I would even go as far as saying, when prices go down in the central valley (Tracy, Modesto …), it’s bad news for the bay area. That’s because many folks there commute daily to the bay area.
