A migrant, part of a caravan of thousands traveling from Central America to the United States, looks at U.S. Border Patrol officers through holes in the border wall between the U.S. and Mexico in Tijuana on Sunday. (Edgard Garrido/Reuters)

At a rally in Mississippi on Monday, President Trump made a scattershot pitch for voters to back incumbent Sen. Cindy Hyde-Smith in this week’s runoff election. Among the subjects he covered was, predictably, immigration.

“Illegal immigration is also deeply unfair to American workers, including African American workers,” Trump said. “My administration will always protect Mississippi workers from unfair and illegal competition. A nation’s first duty is to take care of its own citizens.”

That argument has been an undercurrent to Trump’s rhetoric on immigration from the earliest days of his campaign. It’s a convenient overlap of two issues he focuses on regularly: undocumented immigrants and job creation. But is it something that poses a risk to American workers, especially in Mississippi?

On Tuesday, as Mississippians were headed to the polls, the Pew Research Center released new information that answers that question. Pew regularly assesses the number of immigrants living in the country illegally, determining there are a little under 11 million people living in the United States who meet that description.

That number has been falling in recent years.

(Pew Research Center)

A result is that the density of undocumented immigrants in the workforce has also declined. As a percentage of workers in the labor force, the density of undocumented immigrants was lower in 2016 (the most recent year analyzed by Pew) than in 2005.

(Pew Research Center)

And in Mississippi, there’s an unusually low density of undocumented immigrants in the workforce. According to Pew, 1 percent of the state’s workforce is made up of immigrants in the country illegally. The industry with the largest number of undocumented employees in the state is construction.

(Pew Research Center)

In other words, of the 1.3 million people in Mississippi’s labor force, about 13,000 are undocumented.

What’s particularly interesting about the Pew data, though, is that downward trend over time. The country usually sees declines in the number of employed people during recessions, but during the 1990 and 2001 recessions, both the U.S. labor force and the number of undocumented immigrants in the country increased fairly steadily.

During the recession in 2008, though, the picture was different. The size of the U.S. labor force flattened — and illegal immigration began to reverse.

(Philip Bump/The Washington Post)

That recession had a remarkable effect.

A number of states saw significant decreases in the number of immigrants living there illegally since 2007. In California, more than half a million fewer undocumented immigrants lived in the state during 2016 than had in the previous nine years.

(Pew Research Center)

There are two interesting implications to the new Pew data.

The first is that, even as Trump was running a campaign centered on the risk posed by immigrants in the country illegally, the density of that population was continuing to erode. The number of undocumented immigrants from Mexico in particular — people that Trump, during his campaign launch, suggested were more probably than not criminals — dropped to 5.4 million in 2016, the lowest figure in more than 10 years.

The second is that this, like the employment numbers overall, shows the continuation of a trend that began under President Barack Obama. Pew’s data ends at 2016, so it’s impossible to determine how the population of undocumented immigrants has changed during Trump’s tenure. But if it hit a new low in 2017, as well, that would be yet another continuation of shifts that began during Obama’s presidency.

As for Trump’s rhetoric, there’s now a succinct rejoinder: The density of undocumented immigrants competing for jobs in the United States was lower in 2016 than it has been in at least 11 years.

And in Mississippi, it was less of an issue than nearly anywhere else in the country.