In a much-discussed recent article, our old friend Ron Unz presents his own tables, charts, and correlations in an effort to prove Hispanic immigrants are not the crime-crazed group that many Americans suspect they are. [Ron Unz, His-Panic, The American Conservative, March 2010.]

Matthew Roberts and Steve Burton have already published criticism of this piece in Chronicles, [Unzism, A Dangerous Doctrine, February 22nd, 2010] and Unz has already replied. His-Panic has also gotten a lot of attention from immigration enthusiasts, (Tyler Cowen, Radley Balko of Reason) and even from fairly recent convert to immigration enthusiasm Lew Rockwell.

Unfortunately, Unz' analysis of the immigration/crime link suffers from the same ambiguities and inconsistencies as those he (rightly) dismisses.

More unfortunate still: Unz ignores reliable data showing that Hispanics are rapidly catching up to blacks as the most violent demographic in the U.S.

There is no smoking gun on Hispanic immigrant crime—because official crime and incarceration statistics do not distinguish between immigrant and native-born offenders of any race or ethnicity.

Several academic studies have tried to zero in on immigrant criminality using Census Bureau data. Those too have foundered, mainly because the small sample surveys on which they rely yield wild and unstable trends in immigrant population and incarceration growth.

So what is the crime rate for Hispanic immigrants? In its simplest form, it is the number of incarcerated Hispanic immigrants divided by the total Hispanic immigrant population. Ideally, we would compare this to corresponding rates for native-born whites, blacks, and Hispanics—to determine whether Hispanic immigration increases the overall crime rate.

It sounds simple. But there are big problems.

Most crimes are committed by individuals aged 15 to 44, with the 18 to 29 age range representing a sharp peak in criminal activity. The median age of U.S. Hispanics is around 27, near the peak of the top crime range. But the median for whites is over 40, putting nearly half beyond the range at which crime is likely.

In addition, male inmates outnumber females in U.S. prisons by a ratio of 14 to 1. Since immigrants are (somewhat) more likely to be male, there is a built-in gender bias in immigrant crime statistics.

Adjusting Hispanic and white incarceration rates for age differences reduces the gap by about one-third. Even age-adjusted figures are unreliable if they are restricted to prisoners in federal jurisdiction, where more than half are incarcerated for immigration-related offenses.

Ascertaining a convict's immigration status is even more difficult. Not only are felons reluctant to reveal their county of origin and lack of citizenship, but many localities forbid their police and prison personnel from even asking such questions.

Federal data is not much help. For example, the Census lumps the prison population into a larger category—people living in "Group quarters". But this category includes people in college dorms, nursing homes, and military bases.

Several crime studies confine their analysis to younger men in group quarters, assuming that this is reasonable proxy for those in jails and prisons. But the numbers make no sense: the 74,000 increase in incarcerated immigrants in seven years (2000 to 2007) is larger than the entire immigrant prison population in 2000.

The authors of one recent analysis observe that "If true, the national figures indicate we are in the midst of an immigrant crime wave," warning, however, that "…actually, the recent change in the numbers reflects the enormous problems with the underlying data and almost certainly bears no relationship to reality." [Immigration and Crime: Assessing a Conflicted Issue, By Steven A. Camarota, Jessica Vaughan November 2009]

The FBI's Uniform Crime Report database  records the race of all individuals arrested for crimes. Unfortunately, Hispanic arrestees can be reported as "white", "black", or even "Asian"—rendering the crime data useless for our purpose.

Data on the prison population published by the Bureau of Justice Statistics is better: it carefully records ethnicity (Hispanic/non-Hispanic) as well as race. Accordingly, my go-to source for ethnic crime statistics is BJS's annual analysis of data provided by federal and state correctional authorities.

The most recent such report, published in December 2008, finds that Hispanic males are about 2.5-times more likely to be incarcerated than white males, but only about one-third as likely as Blacks.

While the Hispanic/white differential shrinks somewhat in high-crime age brackets, it remains in the vicinity of two to one:

Mr. Unz takes notice: "So perhaps those fearful commentators are right and Hispanics commit crimes at roughly two-and-a half times the rate of whites in America."

But then he demurs, citing extenuating circumstances of age, gender, and lastly, immigration status:

"…But even these lower figures may still be a bit misleading. As a recent front page New York Times story pointed out, over half of all federal prosecutions these days are for immigration-related offenses, and since a huge fraction of illegal immigrants are from south of the border, the 10 percent or so of U.S. prison inmates who are in federal custody might significantly distort our ethnic imprisonment statistics. Anyway, offenses such as robbery, rape, murder, burglary, assault, and theft are almost always prosecuted in state courts, so it makes sense to separate these street crimes from cases of illegal nannies convicted of illegal nannying."

To which we say: Amen. Our concern with immigrant crime has nothing to do with visa overstayers or even illegal entry per se. We are worried about personal safety.

Surely Unz understands this. Yet he conveniently ignores data that confirms our worst fears regarding Hispanic criminality:

The number of Hispanics serving time for violent crimes increased by 63% in just six years, 2000 to 2006. Over the same period the number of whites incarcerated for such offenses rose by only 7.1%, while the corresponding number of Blacks actually fell by 2%.

 Put differently, Hispanics account for more than half (56%) of the recent increase in violent crime. That is four times larger than their share of the adult population.

NB: Blacks are still far more likely to be incarcerated than Hispanics. There were nearly twice as many blacks in prison for violent crimes in 2006 as Hispanics. But Hispanics are obviously narrowing the gap. The marginal perpetrator of violence in the U.S. is far more likely to be Hispanic than black.

Unz suggests that murder statistics are the most reliable of all:

"A reasonable question arises: are all of these crime rates actual, or might they be statistical artifacts produced by widespread underreporting of crime in heavily Hispanic areas? We cannot absolutely eliminate this possibility, but for homicides the reporting rate is always close to 100 percent, and since for all these cities the homicide and other serious crime rates tend to follow very similar patterns, there is no evidence that any of these racial patterns were warped by substantial underreporting."

But, in fact, nowhere is the Hispanicization of violent crime more evident than in homicides:

Overall, the number of prisoners doing time for murder fell by nearly 8% during the 2000 to 2006 period. The number of whites fell by 35%, the number of Blacks fell about 20%. Only Hispanics bucked the trend: 13,400 more Hispanic murderers were in prison in 2006 than 2000—a whopping 57% increase. As far as murder is concerned, the new boys on the cell block are overwhelmingly Hispanic.

Why? At a time when violent crime is declining across the country, it is hard to imagine U.S.-born Hispanics are fueling the upsurge. But Hispanic immigrants, a group disproportionately composed of males in the high-crime age-brackets who come from a country where violent crime is on the upsurge, are the likely suspects. As Steve Sailer pointed out

"Incarceration rates aren't exactly the same as crime rates. Hispanic immigrants who commit murder are a lot likelier to make a run for the border, on the other side of which are waiting friends and relatives, than are American-born homeboys, especially non-Hispanic blacks and whites.

You can see evidence of this at the Los Angeles Police Department's Most Wanted website. A very large fraction of the LAPD's Most Wanted have foreign first names, suggesting they were foreign-born. "

The Hispanic prisoner boom is a sticky point for immigration enthusiasts. Unz ignores it. Like any good debater, he diverts attention from inconvenient facts by focusing on other relationships which—at first glance—seem to support his thesis:

"Take five minutes to consider the list of America's urban crime rates provided on Wikipedia, and you will notice an intriguing pattern. Nearly all of the most heavily Latino cities have low or even extremely low crime rates, and virtually none have rates much above the national average. Eighty percent Latino El Paso has the lowest homicide and robbery rates of any major city in the continental United States. This is not what we would expect to find if Hispanics had crime rates far higher than whites. Individual cities may certainly have anomalously low crime rates for a variety of reasons, but the overall trend of crime rates compared to ethnicity seems unmistakable."

Get it? To keep America safe we need to flood our cities with Hispanics.

Tell that to the victims of those 13,400 Hispanics recently sentenced for murder.

Reality check: Cities with large Hispanic population shares may indeed have below average crime rates. But this result obtains not because Hispanics are paragons of virtue—but because they are not blacks. A city's overall crime rate is a weighted average of rates for its white, black, and Hispanic residents—the weights being population shares of each group. A higher Hispanic population share usually means a lower Black population share—and a lower overall crime rate.

Blacks are still the main driver of urban crime rates. The incarceration rate of black non-Hispanic males in peak crime ages 18 to 39, for example, is about 16-times that of their foreign-born Mexican counterparts, and twice that of similar U.S.-born Mexicans. [Ruben G. Rumbaut, et al., "Debunking the Myth of Immigrant Criminality: Imprisonment Among First- and Second-Generation Young Men," Migration Policy Institute, June 1, 2006. Table 1.]

So as Hispanics displace blacks in America's largest cities, stable or slightly declining crime rates are not at all surprising. But correlation does not imply causality.

Unz knows this. Yet the main thrust of his article is that the negative correlation between Hispanic population shares and urban crime rates means that Hispanics are, statistically speaking, no different than whites:

"….Taken as a whole, the mass of statistical evidence constitutes strong support for the "null hypothesis," namely that Hispanics have approximately the same crime rates as whites of the same age."

At another place he hedges his bet:

"Admittedly, all of the arguments presented here are somewhat statistical and circumstantial. Correlation does not prove causality, and it might be possible to come up with a complex and detailed set of ad hoc theories and counter-arguments to explain away the vast mass of apparent evidence indicating relatively low Hispanic crime rates. But such an approach places the burden of proof on the wrong side."

However, we do not need "complex and detailed" theories to debunk Ron Unz's benign take on Hispanic criminality.

The simple, easy to understand prison statistics highlighted above do that. At the end of the day, Unz's sophistcated analysis merely proves that Hispanics are not blacks.

He has a point. But it is not the point he wanted to make.

Edwin S. Rubenstein (email him) is President of ESR Research Economic Consultants in Indianapolis.