Harvard economist Greg Mankiw, former chairman of President Bush's Council of Economic Advisers, recently blogged:

"Of all the economists I know, George Borjas of Harvard's Kennedy School is the one most critical of proposals to relax immigration restrictions, such as President Bush's proposed guest worker program."

There's a parsimonious explanation: Dr. Borjas knows more about the effects of immigration than all the other economists Dr. Mankiw knows.

Although economists tend to be willfully ignorant about immigration, Borjas has been an impressive exception.

Now, in collaboration with Jeffrey Grogger and Gordon H. Hanson, Borjas has published an important new paper, "Immigration and African-American Employment Opportunities: The Response of Wages, Employment, and Incarceration to Labor Supply Shocks," on a topic often discussed here at VDARE.com:

Is immigration bad for blacks? 

Perhaps the most tragic American paradox of the last half century is that as the legal and social restrictions hindering black economic advancement diminished and a sizable black middle class emerged, a large fraction of black men dropped out of the workforce and/or went to prison.

The three economists note that from 1960 to 2000:

"The employment rate of black men in the United States fell precipitously from 89.6 percent in 1960 to 76.1 percent in 2000… The decline in labor market participation among black men was accompanied by a rapid increase in the number of black men in correctional institutions. As recently as 1980, only 0.8 percent of black men … were incarcerated. By 2000, 9.6 percent of black men … were incarcerated."

In particular, for black male high school dropouts, the exit from the job market was catastrophic:

"… the employment rate of black high school dropouts fell by 33 percentage points, from 88.6 to 55.7 percent, as compared to an 18 percentage point drop for white high school dropouts, from 94.1 to 76.0 percent."

This isn't the "unemployment rate," but the "employment rate." The more famous unemployment rate doesn't measure those who have given up looking for a job because they are discouraged, lazy, or in jail.

Similarly, the black crime rate shot upwards and, once the soft-on-crime Sixties and Seventies were over, so did the black imprisonment rate:

"As recently as 1980, only 0.8 percent of black men … were incarcerated. By 2000, 9.6 percent of black men … were incarcerated."

For black male high school dropouts, the historic surge in imprisonment staggers the imagination:

"Among [black male] high school dropouts with 1 to 30 years of experience, for example, the incarceration rate was 1.4 percent in 1960, 1.3 percent in 1980, 14.3 percent in 1990, and an astounding 25.1 percent in 2000."

In other words, about one quarter of black male high school dropouts are locked up at any point in time.

Was immigration's depressing effect on wages responsible for this by dissuading less skilled blacks from honest labor?

Borjas has done a sophisticated study. Since 1999, I've been nagging prominent economists such as Steven "The Freakonomist" Levitt and David Card to stop promoting theories (in Levitt's case, that legalizing abortion cut crime and in Card's case, that immigration doesn't reduce wages) that depend on blithely ignoring notorious real world events such as the crack cocaine era of 1987-95 and the Miami powder cocaine boom of the early Eighties, respectively.

Borjas, however, explicitly includes the effect of crack in his model.

Moreover, while Levitt and Card fetishize state/local data,  which allows them to bury their mistakes in reasoning and technique in a blizzard of numbers, Borjas looks both at immigration's impact on black behavior in the individual states and at the national level, which more realistically accounts for the interconnectedness of the national market.

Still, this is a difficult topic to quantify fully. So, before revealing Borjas' findings on immigration's impact on African-Americans, I'm first going to lay out my more casual reasoning to explain why his results strike me as quite plausible.

The costs imposed by the post-1960 moral collapse of the lower stratum of African-Americans have been borne by more than those poor blacks themselves, but by all of American society. Arguably, the decay of the black underclass was the worst disaster suffered by America in the second half of the 20th Century. The heightened number of murders committed by blacks during the great crime wave of roughly 1965 through 1995 is about twice the total American fatality toll in Vietnam.

We more or less lost one great American city, Detroit, which looks today as if all the terrorists in history and imagination had done their worst to it.

Can we blame it all on immigration?

As satisfying as that would be, I've always been skeptical. The historical record suggests that this downfall of the black underclass first began about 1964-65, before immigration became as powerful a force as it has been over the last quarter of a century.

To illustrate broad historical trends, I created in 2005 the Crime Misery Index, modeled on the traditional Economic Misery Index (unemployment rate plus inflation rate) invented by economist Robert Barro.

The idea is to track both crime (the red line indicates homicide victimization per capita, that being the most trustworthy measure of the crime rate because attention must be paid to a dead body) plus the costs we undergo to avoid crime (with the blue line indicating my proxy: the state / federal imprisonment rate per capita.)

The purple line above is the sum of the homicide rate (red line) plus the imprisonment rate (blue line). The averages of the 1950s are set as equal to 100 for both homicide and prison indices, so the combined Crime Misery Index in the 1950s averaged 200.

This Crime Misery Index graph is for all races. The federal government only breaks out homicide rates by race since 1976, but African-Americans have committed a majority of all murders in most years since then, so these overall figures roughly follow the black rates.

As you can see in the Crime Misery graph, in the 1960s the imprisonment rate went down while the murder rate, not coincidentally, shot up, roughly doubling from 1965 to 1975. Eventually in the late 1970s, the prison rate started its long rise. The murder rate dropped a little in the mid-1980s, then rose again to another peak in the early 1990s during the crack wars. The prison rate went through the roof in the 1990s and the murder rate finally dropped significantly.

Although by 2000 the murder rate was almost back down to the good old days of the 1950s, the overall Crime Misery Index remained at a historically unprecedented level due to the huge costs we continue pay to avoid crime.

So, it's unlikely that immigration was the primary initial trigger of the rise in antisocial behavior by poor blacks from 1965 onward. The usual suspects such as more liberal welfare payments and the Warren Court undermining police forces seem more plausible.

A less well-understood cause of the post 1965 crime wave had its roots in the Great Migration of blacks from the South to the North, which peaked after World War II. First generation migrants tend to have moderate crime rates because they typically arrive too old to fall into youth street gangs. Plus, newcomers tend to be intimidated by memories of the harsh policing back home and by the novelty of their new urban environments.

Their sons and grandsons, however, often have much higher crime rates. For example, columnist Linda Chavez recently attempted to defend mass immigration by citing statistics implying that American-born Mexicans are more than eight times more likely to be imprisoned than are Mexican-born Mexicans. (For some reason, she thought this was good news!)

Similarly, the generation of black youth that grew up on the streets of the Northern big cities in the 1960s simply felt more secure about breaking the law than did their more anxious ancestors from the Jim Crow South.

Meanwhile, the Black Pride movement of the 1960s discouraged blacks from taking traditional service jobs, such as waiters, because they now seemed servile and unmanly. (Whether Hispanics might someday experience a similar change of heart is something the American elite never worries about.)

The 1965 Watts Riot signposted the beginning of the crisis of the black underclass and the 1992 South Central Riots denoted its nadir during the crack years.

Since then, fortunately, there has been some recovery among blacks—mostly among black women. Many of their statistical indicators started flickering upward in the early 1990s, and the 1996 cutback in welfare boosted the trend toward black female self-reliance.

So today black men are killing each other in reduced numbers. But they are still going to jail at horrific rates. And their labor force participation remains very bad. In the boom year 1999, 30 percent of younger black men were out of the labor force.

This is where immigration has an effect. It may not have set off the black behavioral decline—but it has made it harder for blacks to recover.

If a young black man of below-average intellect is wavering between a career as a laborer or as a criminal, the wage he would earn doing honest work can play a role in this crucial decision. And, according to the law of supply and demand, that wage must be driven down by the increased supply of labor caused by immigration.

The weaker rebound by black men may well stem from the greater competition suffered by black men at the hands of Hispanic illegal immigrants. First, there are more male than female illegal aliens. Second, lots of black women go into clerical jobs where literacy in English is a prerequisite. Many get government jobs reserved for citizens.

In contrast, black men have more trouble than black women getting high school degrees and learning to read and write adequately, so they are more vulnerable to displacement from blue-collar jobs by illegal alien men.

Borjas notes:

"The comparison of the simulation results for black and white men suggests that the 1980-2000 immigrant influx had roughly similar impacts on wages by race [about an 8 percent cut for high school dropouts], but had a bigger impact on both employment rates and incarceration rates for blacks."

It appears that whites tended to gut it out in the workforce when immigration hurt their wages. Blacks seemed to be more vulnerable to dropping out of the work force and trying their hand at crime.

This fits with other evidence showing that the moral character of the white American working class has been fairly resilient over the last couple of decades, perhaps due to the popularity of fundamentalist Christianity. In contrast, the irreligious white British working class has deteriorated into neo-Hogarthian binge-drinking and property crime.

Borjas concludes, quite reasonably:

"The economic adjustments unleashed by the large 1980-2000 immigrant influx, a labor supply shock that increased the number of workers in the United States by nearly 10 percent and the number of high school dropouts by over 20 percent, reduced the employment rate of black men by about 5.0 percentage points.

He notes the substantial harm immigrant competition has imposed on our black fellow citizens:

Immigration, therefore, accounts for about a third of the 17.1 percentage point decline in black employment rates. Similarly, the changes in economic opportunities caused by the 1980-2000 immigrant influx raised the incarceration rate of black high school dropouts by 1.7 percentage points, accounting for almost 10 percent of the 19.5 percentage point increase observed during that period."

So, immigration didn't start the corrosion suffered by our black fellow citizens, but it has exacerbated it.

As with so many other American social problems, there is an immigration dimension— unexamined except here on VDARE.COM.

[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.]