A standoff between President Donald Trump and Democratic congressional leaders over how to address unauthorized immigration at the U.S.-Mexico border has led to a partial shutdown of the federal government – one that is now the longest on record.

The United States was home to 10.7 million unauthorized immigrants in 2016, a 13% decline from a peak of 12.2 million in 2007, according to the most recent Pew Research Center estimates. This decade-long decline was driven almost entirely by a decrease in unauthorized immigrants from Mexico, even as the numbers from El Salvador, Guatemala and Honduras increased. Meanwhile, a growing share of unauthorized immigrants were not people who had entered the country illegally, but had arrived legally and then overstayed their visas.

More recent data from the federal government show that 2018 saw an uptick in border apprehensions (which are often used as a proxy measure for unlawful entries). There were nearly 467,000 apprehensions at the southwest border last year, the most in any calendar year since at least 2012. Still, the number of apprehensions in 2018 remained far below the more than 1 million apprehensions per fiscal year routinely recorded during the 1980s, 1990s and 2000s.

Read more here for a look at how Americans see illegal immigration and related issues.

Pew Research Center: How Americans See Illegal Immigration, the Border Wall and Political Compromise