Of the 41 million foreign-born people living in the United States in 2012, about 22 million were noncitizens, according to a Congressional Budget Office analysis of Census data. That noncitizen category includes lawful permanent residents (who are legally allowed to live and work here); temporary residents and visitors; and unauthorized residents. That last category includes some 11 million to 12 million people, a number that has stayed fairly constant, the CBO researchers said.
As the 2016 presidential election approaches, conservative candidates have been proposing tough measures to reduce that number, in some cases to zero through an aggressive deportation campaign.
The most vocal proponent—leading Republican candidate Donald Trump—has proposed various measures, including mass deportations, seizure of remittance payments made with illegal wages, raising fees on temporary visas issued to Mexican CEOs and diplomats and other measures.
Trump has also proposed demanding payment from the Mexican government
"The Mexican government has taken the United States to the cleaners," Trump said in a position paper on immigration. "They are responsible for this problem, and they must help pay to clean it up."
It's tough to estimate just how big a bill Trump plans to send to Mexico City—a lot depends on the specific details of any deportation plan. But some researchers have taken a run at the question.
In March, American Action Forum, a center-right policy institute led by former CBO director Douglas Holtz-Eakin, estimated it would take between $100 billion and $300 billion to arrest and remove "all undocumented immigrants residing in the country, a process that we estimate would take 20 years," the group said.
Once those undocumented immigrants had been removed, it would take another $315 billion in higher enforcing costs to keep them from coming back, according to AAF.
That estimate includes just the hard cost of removing undocumented workers; it doesn't take into account the economic impact that would result from the removal of some 11 million people from the labor force and the resulting loss of consumer spending.
AAF estimated the removal of that many people would shrink the pool of U.S. workers by 6.4 percent, which means that 20 years from now the U.S. economy would be nearly 6 percent cent smaller. That works out to a loss of $1.6 trillion in lost wages, spending and other economic activity.
To put that in perspective, the gross domestic product for Texas last year was about $1.5 trillion, second behind California.
While this impact would be felt across the country and throughout the economy, sectors such as agriculture, construction, retail and hospitality would be hardest hit, the AAF report.