This is from John Rosenberg at Discriminations:

Discriminations: Does Colorblind Equality Cause Population Loss?

You probably think I’m joking, but I’m not. A California organization in favor of racial preferences and opposed to colorblind racial equality points to Prop. 209 as causing a drop in the black population of California on “a scale not seen since the Exodus of 1858, when blacks left San Francisco for British Columbia due to the Fugitive Slave Act….”

Who’d a thunk: equality as a form of population control!

One of his commenters noted the violent ethnic cleansing that Mexican gangs are attempting in black neighborhoods, but even without that, "it's the immigration, stupid," that's making blacks and whites leave California for greener pastures.

See In California, Immigration Is The Real Terminator in which Sam Francis quoted an LA Times article to the effect that "More than 1.4 million people in the U.S. migrated to California from 1995 to 2000, while 2.2 million left—the highest migration numbers in the country." More about the impact of immigration from Linda Thom here and from Two Blowhards here.

I'd never heard of the "Exodus of 1858," by the way, it was apparently caused largely by a gold rush on the Fraser River which led to a labor shortage in British Columbia.