One third of illegals are on welfare.
Link? 100% of Americans that are retired on a pension, and receiving Social Security are the recipient of welfare benefits.
Or one sixth of them. Or one ninth. More or less. The numerator is presumably known fairly well. The denominator, however, depends on whose bogus estimates you choose to believe for the number of illegals in the US. On this very thread, we've seen estimates of 10 million, 20+ million, and "over 30 million".