PolitiFact: How many illegal immigrants again?

In a major policy speech on immigration last week, Donald Trump criticized the government's approach to the undocumented population, saying that the feds don't even know the scope of the problem.

"Honestly, we've been hearing that number for years. It's always 11 million. Our government has no idea. It could be 3 million. It could be 30 million," Trump said. "They have no idea what the number is. Frankly, our government has no idea what they're doing on many, many fronts, folks."

Trump questioned the 11 million figure early in his presidential bid last year, and floated 30 million and 34 million as alternative estimates. That claim rates Pants on Fire.

Is it possible that, a year later, Trump's claim of 3 million or 30 million is more accurate?

The answer is still no.

The U.S. Homeland Security Department last estimated the size of the undocumented immigrant population at 11.4 million in January 2012, down from a peak of 12.2 million in 2007. This count includes people who entered the U.S. illegally and people who overstayed their visas.

Figures from independent organizations that study immigration are all in the same ballpark. Unauthorized population size in 2012 and the latest year available, by source:

• Pew Research Center: 11.2 million; 11.3 million (2014).

• Center for Migration Studies: 11.1 million; 10.9 million (2014).

• Center for Immigration Studies: 11 to 12 million; 11.7 million (2016, preliminary).

All of these figures come from subtracting known legal immigrants from the total number of foreign-born people documented in the U.S. census, then controlling for the estimated percentage of unauthorized immigrants who refuse to answer the census.

Researchers at all of the organizations told us Trump's statement is wildly inaccurate.

If the figure really is as high as 30 million, school enrollment and birth registration would reflect that, as both public schooling and birthright citizenship are incentives for undocumented immigrants, pointed out Steven Camarota, research director at the Center for Immigration Studies, which advocates for low levels of legal immigrants.

"But the numbers are not out of whack," Camarota said. "Bottom line is we don't know what the number is for sure. But based on the available evidence, it seems very unlikely that it's 20 million [more]."

Trump suggested he was skeptical of the 11 million figure because it's "always" been the estimate. Experts told us there's a good explanation for that: a steady flow of people coming in and leaving.

"There's enormous churn in the illegal immigration population. Hundreds of thousands come in at 11 million and then hundreds of thousands leave," Camarota said, adding that the undocumented population is a demographically unusual group as it can't grow by births (as all children born in the United States are citizens).

While the federal estimate hasn't been updated in a few years, experts agreed that the outside groups' calculations are sound. Still, Camarota criticized the government for not providing a more recent figure.