Statistics on American emigration

Greetings, all.

Does anyone know of a good (preferably online) source of information on American emigration in modern times? I’m looking for statistics on the emigration rate, destinations, and possibly even reasons for leaving. I suppose the government may not keep official records on this, especially the reason-for-leaving bit, but perhaps some third party has done a study on a randomish sample of emigrants…?

In the absence of statistics, I’d be happy to hear anecdotal evidence from individual Dopers, in which case this thread should probably eventually be moved.

I hope it’s OK to bump this, since it hasn’t gotten any replies yet…

This report, from the Census Bureau, looks at emigration from the United States - the tables included in the report seem more helpful, although I didn’t read the text closely.
There may be something in the Statistical Abstract, but I find the online version more difficult to use than the print version - no real search available, and the print version (any library should have a copy) is indexed, making it easier to find the specific information you need if it’s in there.