Ill-informed and innumerate theorizing about crime trends is a popular pastime among America's ambitious academics and pundits. The latest example: Open Doors Don't Invite Criminals, a March 11th New York Times op-ed by Harvard sociologist Robert J. Sampson claiming that massive Hispanic immigration has reduced America's crime rate in recent years.

It's easy to see why this silly theorizing happens. There are vast and highly un-PC differences in criminal tendencies among the different races—for example, African-Americans wind up in prison an incredible 33 times more often per capita than Asian-Americans. So the Mainstream Media almost never dole out enough information on crime trends to foster understanding.

My favorite example up to now: the popular theory put forward by celebrity economist Steven D. Levitt in his massive 2005 bestseller Freakonomics that the legalization of abortion from 1970-1973 caused the late-1990s crime drop by pre-natally culling future criminals.

Yet, as I pointed out to Levitt when we debated his theory in Slate.com in 1999, he forgot to look at crime rates by the proper age groups. In reality, the crime decline began among those born before the legalization of abortion. Those born in the years after Roe v. Wade went on the worst youth violence binge in recorded American history. Murder rates tripled compared to the cohort born just before legalization. The peak years for murder and other serious violent crimes committed by youths under 18 were 1993 and 1994—more than two decades after Roe.

Additionally, the Freakonomics Factor should have driven the murder rate down fastest among black youth, because according to Levitt and his co-author John J. Donohue in 2001:

"Fertility declines for black women [due to the legalization of abortion] are three times greater than for whites (12 percent compared to 4 percent). Given that homicide rates of black youths are roughly nine times higher than those of white youths, racial differences in the fertility effects of abortion are likely to translate into greater homicide reductions."

But instead, the black male age 14-17 homicide rate was more than 4 times higher among the first cohort born after Roe. Not surprisingly, last year, two economists at the Boston Fed, Christopher Foote and Christopher Goetz, redid Levitt's complex state-by-state statistical analysis and found that he had made two fatal errors. When corrected, his abortion effect vanished.

Another example of silly theorizing: In his bestseller The Tipping Point, Malcolm Gladwell offered his theory of why New York City crime had declined in the 1990s, based on his insight into the marketing concept of tipping points.

You see, and follow me closely here, rising trends, such as crime rates or sneaker sales, tend to go up until they reach a "tipping point," and then they go down. Or vice-versa. Or sometimes they reach a tipping point and then they go up even faster. Or down even faster. It's hard to predict.

If that explanation of tipping points isn't totally clear, you can pay Gladwell $40,000 to come out and explain it at your annual sales conference. (Gladwell and Levitt's co-author Stephen J. Dubner are currently debating each other on their respective blogs. For once, the normally lucratively vague Gladwell may have more specifics on his side.)

Now, along comes Robert J. Sampson's theory in the NYT:

"[E]vidence points to increased immigration as a major factor associated with the lower crime rate of the 1990's (and its recent leveling off)."

This makes Levitt's abortion theory look like Einstein's General Theory of Relativity. I mean, Levitt's theory at least sounds semi-plausible, if you don't actually know the historical facts. But Sampson's is self-evident flapdoodle. It has to be one of the sillier theories ever seen in the New York Times—and that's saying a lot!

Even the headline is hilariously self-refuting: "Open Doors Don't Invite Criminals."

Yes, actually, they do.

The NYT editors should try an experiment—leave the doors to their homes and automobiles open and see what happens.

Why do we see such knuckleheaded arguments in favor of immigration in the prestige press? Because incisive thinking about the subject has been ruled off-limits. If you criticized this op-ed by pointing out that the Hispanic imprisonment rate is 2.9 times the white rate, as reported in The Color of Crime 2005, recently published by Jared Taylor's New Century Foundation, then you are an evil racist and nobody should listen to you. The Establishment's most effective ploy in eliminating debate over immigration has been to insinuate that only shallow (or sick) people think deeply about immigration.

Sampson presents the following graph to show that immigration flows were negatively correlated with homicides in the 1990s.

My response:

• First, even if all immigrants were utterly law-abiding, only the homicide rate would fall—not the total number of homicides, as shown on this graph.

• Second, immigration wasn't sizable enough to even theoretically account for much of the decline in the crime rate. According to Sampson, net immigration per year was running at about a half percent of the American population in the mid 1990s. So, if every single immigrant were a crime-free saint, then the homicide rate would fall a half percent per year. But the total number of homicides was falling more than an order of magnitude faster. (In fact, of course, immigrants aren't all saints, as the vicious Salvadoran Mara Salvatrucha gang shows.)

• Third, Sampson's contention that the slight decline in the rate of immigration in this decade has contributed to the rise in homicides is even more irrational. He's confusing the rate of new immigrants entering the country with the stock of immigrants already in the country, which is the only number that might even theoretically impact the murder rate. Sampson's theory would only work if every time a new immigrant disembarks from his plane at JFK airport, somewhere in America a murderer stays his hand.

That's just magical thinking, voodoo sociology.

To further confuse his readers, Sampson then offers his "Hispanic Paradox:"

"Hispanic Americans do better on a range of various social indicators—including propensity to violence—than one would expect given their socioeconomic disadvantages."

That may or may not be true. But the bottom line is that Hispanic socioeconomic disadvantages are so severe—for example, Robert J. Samuelson wrote in an excellent Washington Post op-ed last week: "The median net worth of Hispanic households is about 9 percent of that of non-Hispanic whites"—that the Latino imprisonment rate is 2.9 times the white average.

Sampson's logic is similar to saying, "Adjusted for height, Congo Pygmies are better basketball players than North Carolinians." Well, that's … interesting, but college basketball coaches would still be better off recruiting in the Tidewater than in the Mbuti rainforest.

Now, it's mathematically possible that an influx of Mexicans, with their high crime rates, can marginally lower the overall crime rate in a city, such as New York, by "economically cleansing" blacks, with their extremely high crime rates. If blacks flee New York because Mexicans are taking their jobs and causing rents to go up, that could make the New York crime rate go down.

Of course, on the national level, Mexican immigration just raises the crime rate because African-Americans have to go somewhere else in our country. (But you can see why Mexicans driving blacks from New York to other cities would appeal to the self-interest of the editors of the New York Times.)

Sampson does tell us one useful thing: all else being equal, propensity toward violence increases as immigrants assimilate:

"Indeed, the first-generation immigrants (those born outside the United States) in our study were 45 percent less likely to commit violence than were third-generation Americans, adjusting for family and neighborhood background. Second-generation immigrants were 22 percent less likely to commit violence than the third generation."

In other words, Hispanic immigrants tend to assimilate toward African-American norms of violence unless they soar upwards economically and educationally. Many do. But many don't.

This isn't surprising. New immigrants often arrive too old to join youth gangs and they are scared of deportation. But their American-born sons grow up on the streets feeling much more confident, and much more territorial about their native neighborhoods. The gangs, like the 18th Street Gang in LA, get the American-born ones young. As "Color of Crime 2005" reports, "Hispanics are 19 times more likely than whites to be members of youth gangs."

So, by importing vast numbers of Hispanic immigrants now, according to Sampson's data, we're just making an unholy mess for ourselves in the future.

Finally, Sampson [send him mail] is wrong about Hispanic immigrants being the cause of lower violent crime rates because we know which ethnic group contributed primarily to the recent decline in homicides—and it wasn't Latinos.

No, it was the same group that also contributed the most to the previous rapid rise in murders from 1984 to 1991: African-Americans. They commit a little over half the murders in America.

Here's a graph of the homicide offending rates from the Bureau of Justice Statistics.

Please note that in order to minimize public awareness of Hispanic criminality, the federal government, which is otherwise so careful to break Hispanics out separately in its statistics, counts all Hispanic murderers as "Whites." So we can't learn anything from federal statistics about Hispanic murder rates. All we know is that the actual non-Hispanic white rate is even lower than shown in the graph. (Ask the federal government why it does this.)

What you can see is that the black murder rate rises and falls much faster than the white/Hispanic rate. This is probably due to convulsions in the drug markets. The worst year of the powder cocaine dealers' wars was 1980. It was followed by a sharp decline in the black murder rate that reversed when the crack cocaine wars began. They peaked in 1990-1994 and then were followed by a sizable decline, which, unfortunately, has bottomed out in this decade.

In terms of number of murders, the low in recent decades was 1984, at 20,337 homicides across all races. From 1984 up through the peak year for murders in 1991 (at 28,268), blacks accounted for 84 percent of the rise in homicides committed.

Then, from 1991 until the low year in 1999 (at 17,402 murders), blacks, who make up only 13 percent of the population, contributed 65 percent of the decline in murders.

So, what did actually cause violent crime to drop—especially in New York City?

An overlooked explanation was brought up by Newhouse News reporter Jonathan Tilove recently: there are today in New York City, 36 percent more black women alive than black men. Nationally, there are now 26 percent more black women than men. In contrast, among the total population, there are just 8 percent more women than men alive.

Tilove wrote:

"In the March/April issue of Health Affairs, Dr. David Satcher, surgeon general under former President Bill Clinton, … exposes the core of the problem: Between 1960 and 2000, the disparity between mortality rates for black and white women narrowed while the disparity between the rates for black and white men grew wider. Exponentially higher homicide and AIDS rates play their part, especially among younger black men." [Where have all the black men gone?  May 08, 2005]

Obviously, this gigantic black male shortage in NYC wasn't caused by abortion or by immigration—there was virtually no sex selective abortion at the time. No, it was mostly caused by an enormous increase in imprisonment and by the most dangerous black men murdering each other in large quantities in the late 1980s and early 1990s. (AIDS played a role too in killing off drug addicts.)

Freakonomics' Levitt has never written, as far as I know, about the impact of these "selective post-natal abortions," as it were, on the crime rate. But it's clearly a substantial factor in a number of big cities that were hit hard by crack.

Moreover, as I pointed out to Levitt in 1999—and as his deservedly famous chapter in Freakonomics on how dealing crack pays so badly confirmed—a lot of the next cohort of urban youths, those born more than a half decade after abortion was legalized in their state, figured out that dealing crack was a stupid career choice. Seeing how their older brothers and cousins wind up in prisons, wheelchairs, and cemeteries, they became less likely to commit murder.

Participating in the crack wars turned out to be, for the vast majority of the gangstas, extremely bad life choices. It's hardly surprising that the later cohort, born in the early 1980s, did a better job of figuring this out.

So, the good news is that poor teens in the ghetto can eventually figure out the difference between smart and stupid.

The bad news, as exemplified by Professor Sampson's op-ed, is that the Harvard faculty and the New York Times can't.

[Steve Sailer [email him] is founder of the Human Biodiversity Institute and movie critic for The American Conservative. His website www.iSteve.blogspot.com features his daily blog.]