Sen. Ted Cruz says there will be “20 or 30 million” people living in the U.S. illegally “in another 10, 20 years” if the Senate immigration bill becomes law. But the nonpartisan Congressional Budget Office says the bill, if enacted, will reduce future illegal immigration by 33 percent to 50 percent compared with current law.

The Republican freshman senator from Texas offered his estimate on ABC’s “This Week,” while discussing the impact of the bill on the political future of one of its sponsors, Republican Sen. Marco Rubio.

Cruz, July 21: If the Gang of Eight bill became the law, in another 10, 20 years, we wouldn’t have 11 million people here illegally, we’d have 20 or 30 million.

We asked the senator’s office to support that statement. His spokesman, Sean Rushton, said that “it was not a factual statement — it was an opinion.”

Rushton, July 23: Senator Cruz’s statement cannot possibly be fact-checked, because it was not a factual statement — it was an opinion. Sen. Cruz obviously cannot cite any “facts” about what the level of illegal immigration will be in 10 or 20 years. He made a prediction about future levels of illegal immigration based on contingent future events, so there are no data that can prove or disprove this statement. Any attempt to assess the truth or falsity of this statement would simply be political editorializing, rather than an assessment of the validity of empirical, factual statements about the world as it exists today.

Nobody can predict the future, but there is a nonpartisan congressional office that produces reports for members of Congress to consider when making policy decisions. We’re referring, of course, to the Congressional Budget Office, which was created by Congress in 1974 to provide “impartial information about budgetary and economic issues,” CBO says. And CBO estimates that in 10 years there would be 6.4 million “future unauthorized residents” without the legislation and 4 million with it — a “net decline in future unauthorized residents” of 37.5 percent.

We arrived at those numbers by reviewing two different CBO reports.

In a June 18 report, CBO said on table 2 (page 15) that there would be a “net decline in future unauthorized residents” of 1.6 million by 2023 and 2.5 million by 2033 under the bill as approved by the Senate Judiciary Committee. That report also said “the net annual flow of unauthorized residents would decrease by about 25 percent relative to what would occur under current law.” That means the CBO projects there would be 6.4 million more residents living in the U.S. illegally in 2023 and 10 million more in 2033 under current law, but those numbers would drop to 4.8 million in 2023 and 7.5 million in 2033 under the bill as approved by the committee.

That’s far less than the “20 or 30 million” people that Cruz says will be living illegally in the U.S. “in another 10, 20 years” if the Senate immigration bill becomes law.

But that’s not all. The bill was amended on the Senate floor to add more funds for border security, and as a result, CBO, in a July 3 letter to the committee chairman, said “the number of unauthorized residents in 2023 would be lower by about 800,000.”

So, CBO now projects the total “net decline in future unauthorized residents” would be 2.4 million by 2023 if the latest version of the Senate bill becomes law. That means, in 10 years there would be 4 million “future unauthorized residents” under the Senate-passed bill — a “net decline in future unauthorized residents” of 37.5 percent from the 6.4 million CBO projects under current law. (The CBO did not provide a revised figure for 2033.)

These are not facts, but they are projections from the nonpartisan source Congress uses in making policy decisions. And these projections indicate that Cruz’s statement is way off base.

After saying there is “no data that can prove or disprove this statement,” Rushton went on to say that the senator’s figures are conservative — if you consider what happened after the last time the nation overhauled the immigration laws, in 1986. He’s referring to the Immigration Reform and Control Act of 1986, which was signed into law by President Ronald Reagan and provided legal status to about 3 million people who had been living in the U.S. illegally.

Rushton, July 23: Basic arithmetic shows that in the 27 years after the United States offered amnesty to those here illegally without guaranteeing border security, illegal immigration increased by 367% — from 3 million to 11 million. … A 367% increase in illegal immigration from the current 11 million would equal just over 40 million. Senator Cruz’s statement predicted that level would rise to 20 or 30 million, so it’s a conservative estimate based on historical experience.

Rushton’s math is wrong and his logic is lacking.

True, there are about 11 million people living in the U.S. illegally. The Pew Hispanic Center estimates there were 11.1 million people living in the U.S. illegally in 2011, down from 12 million in 2007. And it is widely accepted — including by the Senate Judiciary Committee — that the 1986 immigration law resulted in the legalization of about 3 million people. So those figures are correct. But that’s a 267 percent increase from 1986, not 367 percent.

More important, Rushton’s logic assumes the conditions for illegal immigration are the same today as they were in 1986 and that will result in the same outcome. That’s a flawed assumption.

Let’s consider border security. In 1986, there were 3,000 border agents in the Southwest and “technology at that time consisted literally of hand held flashlights, Vietnam-era sensors, very little lighting on the border, and certainly none of the outstanding technology that our agents work with today,” according to the May 22 congressional testimony of David V. Aguilar, a retired acting commissioner of the U.S. Customs and Border Protection who said he “spent 35 years working the borders of our country at many levels within the organizations responsible for the security of those borders.”

Today, he said, the nation has “unprecedented resources” at the border. Aguilar testified that there are more than 21,000 border patrol agents, “the highest level in its 88-year history”; there are more than 650 miles of border fence; and technology includes “integrated fixed towers, mobile surveillance units, and thermal imaging systems.”

The Senate-passed bill would double those numbers, adding 20,000 border agents and 700 miles of fencing, as a result of an amendment passed on the Senate floor by a 69-29 vote with Republican support.

And, as we saw in the CBO projections, enhancing border security is expected to make a difference in the flow of immigrants who cross the border illegally in the future.

— Eugene Kiely, with Madeleine Stevens