Attorney General Jeff Sessions says the Trump administration's tough approach on illegal immigration is the result of a crisis: a mass influx of people coming in over the country's southwestern border.

“We are not going to let this country be overwhelmed,” Sessions said in a May 7 speech  announcing a new "zero-tolerance" policy on southwestern border crossings. "People are not going to caravan or otherwise stampede our border."

Among the effects of that policy is a surge in the number of undocumented children at the border who have been separated from families as their parents are accused of and being prosecuted for illegal immigration. That has led to children being detained in cages and tent cities, reports of staff members being prevented from physically comforting small children and distraught parents killing themselves in detention centers.

But while all this is happening in the name of deterring a “stampede” at the border, federal data reveals the stampede is not happening.

The harsh new rules are necessary because of “massive increases in illegal crossings in recent months,” Sessions said in May. He then laid out some numbers. “This February saw 55 percent more border apprehensions than last February,” he said. “This March saw triple the number from last March. April saw triple the number last April.”

Strictly speaking, the year-over-year figures Sessions cites are accurate. But Customs and Border Protection's own data — showing migrant apprehensions at the southwestern border remain near historic lows -- severely undercut these claims. Border apprehensions are up year-over-year in part because they dropped dramatically in the first few months of Trump's term. And they remain very low by historic standards, as this chart of CBP's monthly Southwest border apprehension data shows.

Throughout much of the 2000s, monthly apprehension totals in the neighborhood of 100,000 people or more were not uncommon. But the last time apprehensions were at that level was more than a decade ago, in 2007.

This chart, showing calendar year-to-date apprehensions for 2000 through 2018, makes that even clearer. The “massive increase” in crossings this year brought apprehensions up to a level not seen since . . . 2014. The 168,659 apprehensions so far in 2017 are less than one-fifth of apprehensions over the same period in 2000.

We can look at CBP's annual apprehension data for an even longer view. The 303,916 undocumented immigrant apprehensions in fiscal year 2017 were the lowest in 46 years. For fiscal year 2018, year-to-date apprehensions are up by about 12 percent compared with last year. If that rate holds steady for the remaining four months of the fiscal year, we will end up with somewhere around 341,000 total apprehensions for the fiscal year, or the fourth-lowest number in more than four decades.

Contrary to Sessions's assertion, in other words, the country is in very little danger of being “overwhelmed.”