I wouldn't be surprised if the unemployment rate of law school grads is just slightly less than the national rate.
It would be really shocking if 18/40 were unemployed annually. Irrx is right on with what he said about response rates. I think of all the surveys my company emails me that go straight to the trash. Those would only take like 30 seconds to fill out.
I think responding to these posts is a better way to spend that time.