For the second month in a row, the number of individuals caught trying to enter the U.S. illegally at the southwest border declined, drawing praise from administration officials who say it is directly tied to President Donald Trump’s zero-tolerance initiative.

In the month of July, border apprehensions declined by 7 percent, according to data released by Customs and Border Protection on Wednesday. In July, a total of 31,303 individuals were apprehended compared to 34,095 in June and 40,333 in May.

The data also shows that fewer unaccompanied minors were arrested at the southern border this month compared to June. In July, 3,938 unaccompanied minors were arrested; in June, the number was 5,093.

Homeland Security Department Spokesman Tyler Q. Houlton credited July’s low border apprehension number to Trump’s recent zero-tolerance initiative that prosecutes individuals caught entering the U.S. illegally, including those with children.

“This decrease shows that when there are real consequences for breaking the law, the conduct of those considering crimes will change,” he said in a statement Wednesday.

But long-term data about southwest border apprehensions also tell a story of declining numbers.

Monthly apprehensions always are highest, going back as far as to 2007, in the cool spring months of April, May and June, when migrant flows to the border tend to be highest. Then they level off in the hotter months of the summer.

And, going back to 2006, border apprehensions have been trending downward. In recent history, 2000 was the peak year for apprehensions of illegal aliens at the border, with 1.6 million caught. In subsequent years, through 2006, about 1 million per year were apprehended.

Then in 2007, steep declines became the rule, triggered in part by the Great Recession that began to grip the United States in 2008 and 2009, which made jobs less available for economic migrants. In 2007, 876,000 apprehensions were made, going down every year through 2011 to a low of 340,000.

Through the next few years, toward the end of the Obama administration, 2012 to 2016, the annual numbers climbed to levels around 400,000, when more people came with children trying to escape the violence in Central America.

In 2017 the number dropped to 310,000, the lowest since 2000.

The current trend of children and families crossing the border in greater numbers began in 2014, when tens of thousands of unaccompanied minors from the Northern Triangle countries of El Salvador, Guatemala and Honduras arrived at the border seeking asylum from gang violence and poverty. Both the Obama and Trump administrations have sought to deter such migrants from making the dangerous journey north.

Jacob L. Vigdor, a professor at the University of Washington who studies immigration, says the long-term declines were because of the lengthy U.S. recession.

“Historically speaking a lot of people that have crossed the border are interested in working. In 2007, the jobs started to dry up, and even though the economy has recovered since then, there has been relatively weak job growth in the United States,” he said Wednesday.

Vigdor says Mexico’s economy also played a big factor in the consistent drop in border apprehension levels throughout the years as the North American Free Trade Agreement created more jobs for people in Mexico.

Tom Jawetz, vice president of immigration policy at the left-leaning Center for American Progress, believes that July’s low border apprehension rates are a direct result of seasonal trends rather than the zero-tolerance initiative.

“There is no evidence that there is a correlation between low border apprehensions to the zero-tolerance policy,” he said. “The administration has proven since day one that they have no problem lying to the American public and when it comes to immigration they have no problem fabricating stories.”

July border apprehension numbers were the lowest since October 2017, when officials apprehended 25,484 individuals, which was before the zero-tolerance initiative was put in place.

Although it is unclear if the zero-tolerance initiative played a direct role in July’s low border apprehension levels, Houlton from Homeland Security called on Congress to pass legislation to fix the immigration system.

“Despite our terribly broken immigration laws, the administration has still been able to impact illegal immigration — but we need Congress to act to fix our system,” he said. “The inability to apply consequences to any law breaker ultimately threatens the safety and security of the nation and its communities.”

Trump’s zero-tolerance initiative was met with a barrage of criticism from advocacy groups and lawmakers from both parties after it forcibly separated more than 2,300 immigrant families at the southern border.

So far, government officials have reunited more than 1,400 children with their parents, but more than 700 children remain in government custody and more than 400 parents were deported without their children, leaving the family separation crisis far from over.