Weird. Why do I keep seeing 4-5 million in the press as the number of people waiting for green cards?
The 30-40 million comes from the fact that there are lot more people who would come to the US that haven't bothered to apply. If you relaxed the criteria the number of applicants would expand.
I'm not anti-immigration (I'm Canadian and we're slightly more relaxed about immigration) but there needs to be some controls in place.