IMMIGRATION SKEPTICS are fond of portraying the southwestern border as lawless and violent, a sort of Spanish-accented version of Pakistan’s tribal areas. In this fantasy dystopia, cascades of illegal immigrants cross the frontier, running roughshod over outmanned and outgunned U.S. Border Patrol agents.

It’s a colorful narrative, designed to scare Americans while deflecting reform of the nation’s broken immigration system. How can we discuss sweeping change, let alone amnesty for millions of undocumented immigrants, the purveyors of fear argue, while chaos reigns along the border?

But the lawless border portrayed by lawmakers such as Rep. Lamar Smith of Texas and Sen. John McCain of Arizona, border state Republicans, is a fairy tale. Illegal border crossings have nose-dived to their lowest levels in many years and are projected to plunge even further. Many segments of the southwest border are so quiet that border patrol agents spend their days surveying barren landscapes devoid of activity.

What’s more, as a recent New York Times article illustrated, the shrinking demand to sneak across the border from Mexico is not only a function of America’s anemic economy, tougher state laws on illegal immigration or the 17,700 Border Patrol agents assigned there, nearly double the number in 2004. It can be traced also to economic, demographic and policy shifts inside Mexico itself.

In fact, such a broad array of factors is depressing the rate of illegal immigration from Mexico that even a surge in the American economy is not apt to drive the numbers of undocumented border crossers back up to the levels of the early- to mid-2000s, when a half million or more flooded into the country each year.

Those factors include sharply dwindling Mexican fertility rates and family sizes, which have shrunk the numbers of potential job seekers; higher gross domestic product and family incomes, which have expanded incentives for Mexicans to make a living at home; and rising educational levels, which are broadening hope and opportunities for Mexicans who want to move up the economic ladder.

At the same time, the Times reported, U.S. consular officials in Mexico have eased rules governing the issuance of tourist and temporary agricultural visas, meaning that thousands more Mexicans are able to enter the United States legally. Rejection rates for Mexicans seeking tourist visas have fallen to just 11 percent from 32 percent before 2008, the Times reported..

Those are salutary trends. Another development — less positive but equally effective at dissuading the undocumented — is the growth of violent Mexican drug cartels that prey on migrants as they head north for the border. As reported by The Post’s William Booth and Nick Miroff, migrants from Central America have been particular targets of the cartels, which have murdered some and press-ganged others into service. Many Central Americans now think it is too dangerous to attempt to cross Mexico into the United States.

The southwest border is hardly watertight; few international land boundaries are. But all indications, including plummeting apprehensions by the beefed-up Border Patrol, are that illegal border crossings have been cut in half in the past five or six years.

The effect of all this must be depressing for peddlers of anecdotes and spinners of tall tales about the border. But the plain facts are simply are not as hair-raising as anti-illegal-immigration Republicans would have Americans believe. Like it or not, the border is a much safer and better monitored place than it has been in many years, and the trend lines promise more of the same.