Chart Of Number Of US Children Born To Illegal Immigrants: 1992-2013

From The Wall Street Journal, "Fact-Checking the Figures on ‘Anchor Babies’: Note to presidential candidates: Estimate of some 400,000 such births is outdated" by Jo Craven McGinty:

Still, the numbers disturb Mr. Trump and others who favor cracking down on illegal immigration because as citizens, these children automatically get access to education, health care and other services. At age 21, they can also apply for legal status for their undocumented parents and siblings, which is why critics refer to them as anchors.

For those and other reasons, different groups have tried to pin down their number. The Migration Policy Institute, the Center for Migration Studies and the Pew Research Center, in addition to the Center for Immigration Studies, have all published estimates.

The figures peaked in 2007-10. In that span, the Migration Policy Institute put the high number at 321,000; the Center for Migration Study pegged it at just under 350,000; and the Pew Research Center put it at 370,000.

The numbers vary because each group uses a slightly different approach.***

Source: The Wall Street Journal