On immigration, it seems, the conservatives' principle is conservation of anti-immigration bias. If they tamp down animus against one set of immigrants, then they must whip it up against another.

How else to explain the gratuitous swipe against “chain migration” in an otherwise excellent commentary in The Wall Street Journal last week by Jeb Bush and Clint Bolick debunking virtually every other immigration myth on the right?

While calling for more employment-based immigration, creditably for both skilled and unskilled foreign workers, Bush and Bolick maintained that since the 1960s, thanks to American emphasis on family reunification, the driver of immigration to the U.S. has been “chain migration,” which purportedly allows immigrants to bring in their extended families until entire villages are emptied out.  

But “chain migration” is a myth cooked up by ultra-restrictionist organizations, such as NumbersUSA, that foster misunderstanding about how U.S. laws work and undermine more-welcoming policies.

According to NumbersUSA, chain migration results in “endless and often-snowballing chains of foreign nationals who are allowed to immigrate because the law allows citizens and lawful permanent residents to bring in their extended, non-nuclear family members.” And these family members bring in still more people, creating a chain reaction.

Seriously? Consider the facts.

There is no provision in U.S. immigration laws for either permanent residents (green-card holders) or American citizens to sponsor non-nuclear relatives such as aunts, uncles, nieces, nephews, grandchildren, grandparents, cousins—you name it—to come to the U.S. Other than immediate family members, such as spouses, parents and minor children, the only relatives who can be sponsored are adult children and siblings. That’s it.

And the wait times—thanks to backlogs created by quotas upon quotas—in those two categories are so long that they have become virtually unusable.

A 2011 study by the pro-immigration National Foundation for American Policy found that the wait time for a U.S. citizen to bring a brother or sister from the Philippines exceeded 20 years, and from Mexico 15 years, because these countries get the same annual quota as every other nation yet the demand for them is much greater, creating backlogs. For siblings from other countries, the wait time is about a decade—a little less for adult unmarried children, and a little more for married ones.

Consider the predicament of the 25-year-old foreign wife of a U.S. citizen who wants to bring her 24-year-old brother into the country: It would take her about a year to obtain her green card once she got married. After that, the quickest route would begin with the five-year wait to obtain her citizenship.

At about 31, she would be able to sponsor her brother, now 30, and his family, if any. If the brother is from the Philippines, he would have to wait until he was 50 before he had a prayer of getting a green card; or 45 if from Mexico, and 40 if from some other country. Most people have built lives for themselves in their home country by that age and, when their turn comes, they opt out.

If the brother and his family still decided to immigrate to the U.S., then they would have to go through about the same 20- to 30-year process to sponsor their own next of kin. Over 50 years, then, most families have time to traverse at best two links in the migration “chain.” It is no surprise that siblings of U.S. citizens constitute only 6 percent of immigrants legally admitted every year and adult children 2 percent.  

It is true that 65 percent of foreigners admitted annually are under the family program, rather than the one based on employment. More than half of them, however, are the spouses and minor children of U.S. citizens. Hence, curbing family-based immigration would require breaking apart families. Saying so openly would make Republicans look heartless—which is why they are resorting to baseless claims about “chain migration.”

The more humane and rational way of bringing balance between family- and employment-based immigration isn't by clamping down on the former—but increasing the latter. It would be a real tragedy if immigration reform turns into a zero-sum game.

This column originally appeared in Bloomberg View.