I should add that I find data quite convincing. I hear arguments like the one you state but I don't find them convincing.

This is for several reasons:

1. Saudis feel quite unwelcome in the US, and prefer to buy homes in London.

2. New York is so far that a Chinese billionaire would prefer something on the other coast. Especially in Canada where they don't have to pay taxes on worldwide income if they establish residence.

And without data, this is just an impression based on fragments of articles. I still haven't seen data for the Chinese buyers in Vancouver, and that is a far easier case to make.

...who'd be collating that race data on homebuyers?

Good luck. Link it if you find it.