US Median household income from 1967-2008 by race

[Verily]

Why are Asians hit so hard (relative to the other races) by recessions?

Because they're disproportionately represented in recession-prone industries like IT, middle management, law, etc. Blue collar labor is hit disproportionately less by recessions in terms of job losses (although the blue collar sector has the lowest base job gain outside of recessions, so they still lose a lot of jobs).