The portion of them that deal drugs and collect welfare really are just sub-human leeches --- whatever portion of them are that are --- Over a third are collecting some or many kinds of welfare and a fairly high number are smuggling and dealing in drugs. Those engaging in felony document fraud, using stolen identities and social security numbers are criminals --- sub human leeches. Those otherwise honest types --- who might be working hard for cash and aren't committing other crimes would be in another category.
I assert that it is much less than all 20 million.