A while after the last census came out, some mainstream university economists recalculated the number of illegal aliens using employment figures...
But Paul Harrington of Northeastern
, using his own formula to capture the undercount, thinks the census missed as many as 7 million undocumented immigrants, which he termed a "conservative" figure. By his accounting, illegal immigrants in the United States total 13 million, or 4.6 percent of the population. [Immigrant Tally Doubles In Census
By Aaron Zitner ,Los Angeles Times, march 10, 2001 ]
But that was in 2001. Figuring 3 million additional per year (according to Time magazine)
we get around 20 million
, using advanced calculations involving fingers.