Alex responds to the questions I asked him yesterday.  Read the whole thing, but here are my original three questions, with summaries of his answers in blockquotes:

1. How much higher would cumulative Mexican immigration since 1986 have
been if the IRCA’s employer sanctions hadn’t been imposed?

Temporary migration would’ve been higher AND more illegal immigrants would have permanently settled in the United States.

2. How
much higher would cumulative Mexican immigration since 1986 have been
if the IRCA’s border security boost hadn’t been imposed?  (Your comments
seem to suggest that it actually would have been lower, since guest workers wouldn’t have bothered to bring their families).

Temporary Mexican migration would’ve been higher, BUT fewer of them would’ve settled here permanently.

3. How much higher would cumulative Mexican immigration since 1986 have been if the IRCA’s hadn’t been passed at all?

More Mexican workers would’ve migrated BUT many fewer of them
would have permanently settled here as immigrants.  The circular flow of
1965-1986 would have continued and probably increased. Without the amnesty, there would’ve been roughly 2.7 million fewer Mexicans with green cards, which would’ve meant many fewer green cards for Mexicans in the future.

Alex closes with a question I was coincidentally planning on addressing: “If the benefits of immigration are as great as we like to argue, why are there so few illegal immigrants?”  Answer coming soon!

P.S. My online immigration class starts tonight at 9 PM EST.