Tim Kane is the JP Conte Fellow in Immigration Studies at the Hoover Institution at Stanford University. His most recent book is " Balance: The Economics of Great Powers from Ancient Rome to Modern America " (Simon and Schuster), co-authored with Glenn Hubbard. The views expressed in this commentary are his own.

(CNN) Is the federal crackdown on illegal immigration having a deterrent effect? Or are we suddenly experiencing a calm before the storm?

Newly announced data from US Customs and Border Protection show an "unprecedented decline in traffic," according to a statement Wednesday from Homeland Security chief John Kelly. He never mentioned deportations; rather it was about deterrence.

Critics say the Trump administration's crackdown has been cruel. But its proponents will celebrate the new data as the quick result of decisive action. We'll see.

It is, actually, too soon to pass judgment of any kind. First, Kelly's goals to stem the immigration tide can hardly be called cruel if, as he says , "many fewer people are putting themselves and their families at risk of exploitation, assault and injury by human traffickers and the physical dangers of the treacherous journey north."

Second, the unprecedented decline may be an illusion.

I'm not saying that the 40% drop in apprehensions at the southwest border from January to February is based on bad information. I'm saying it lacks context.

Looking at all the data for the past five years, February apprehensions ranged from 32,000 to 42,000, but this year there were 23,589. That's significantly lower, but January apprehensions were about 10,000 higher this year than in years before. And December apprehensions were 58,478, nearly double the norm.

There are many potential explanations, including temporary weather patterns and source country conditions, but the data seem less indicative of a change in trend than a one-time shift.

Imagine you're an illiterate single parent in an impoverished Central American city that is rife with violence (the situation is different for Mexicans, despite northern stereotypes, who have better access to the middle class and to education). You may have decided that 2017 is the year to try to take the journey north, but you have heard that the new American president, Donald Trump, will build a wall. You decide to go now before the wall gets built.

That kind of thinking may well have pulled tens of thousands of this year's migrants to accelerate their journey, leaving in the winter instead of the spring. That could be what the data indicate. Of course, it will take years for a wall to be built and new enforcement agents to be hired, but that delay is a potential accelerant to border crossings, not a deterrent.

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The deterrent on immigration will be the change in internal enforcement, not the wall. Remember, the Trump administration has done much more than talk tough, and it has not been hypocritical. The president has announced three executive actions relating to immigration -- two on January 25 and a third on January 27.

Only the travel ban was stayed by the courts, but it has already been supplanted by a more focused executive order that seems to be fully within the President's authority to prioritize refugee policy. Trump's orders to deter sanctuary cities, prioritize deportations and empower local officials are proceeding apace.

To be clear, none of those make crossing the border harder. Not yet. But they do make residing in the United States much more difficult. I suspect that deterrence will have an effect.

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Some will say the apprehensions data is faulty because migrants are simply getting better at undetected entry. And it could well be that the Obama administration's deferred action programs granting temporary amnesty to undocumented children brought into the country without authorization (in 2012) and parents (2014) encouraged the refugee surge at the border in 2014, which then distorted the apprehension counts in 2015 and 2016.

Secretary Kelly also asserted this week that coyote's have increased their smuggling fees by as much as 130% in some regions since the US elections in November, which seems to reflect the new administration's stronger enforcement and detention policies. But as any economics 101 student can tell you, higher prices often signal higher demand.

Just maybe the surge in migrants over the winter was the trend, and the February data was an exception. We will know for sure in a few months.

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There may well be another, much larger, force driving these numbers that has nothing to do with the immigration policy in Washington, per se.

Research by University of California, San Diego Professor Gordon Hanson and others shows that the main driver of immigration is relative quality of life. It is noteworthy, then, that since November, the Mexican peso has been under tremendous pressure, eroding real incomes south of the border.

"The Mexican peso is near an all-time low and Trump is a major reason why," warned CNNMoney's Patrick Gillespie in January. If the Trump administration wants to avoid a surge of poor migrants at the border, it should think twice about breaking up the trade agreements with Mexico (NAFTA) and Central America (CAFTA).

Just maybe the wiser heads in the White House will prevail and work toward a deeper trade alliance for the region. A stronger Mexican (and Honduran, Salvadoran, Guatemalan ...) economy will benefit the United States in more ways than one.