I wouldn't say the number of Cauasian SPs have shrunk - albeit, their establishments have - these girls have just gone indie. When we look at the number of SPs on non-Craigslist websites (eg. Eros, Escorts-Canada), we find the vast majority are white girls.
Also, I think competition and not LE has resulted in many non-AMPs to close down. When an AMP charges $120-$150 for FS, how can the white MPs survive w/ rates starting at $180 + up and w/ substandard service (eg. no facials, no DATY for many, no CIM, no BBBJ, lousy massage)? It's just economics.