At least when it comes to crime. Indeed, it matters a great deal more than a host of other social statistics that putatively lead to criminality. In the abstract to the second edition of The Color of Crime, the American Renaissance wrote that "The single best indicator of violent crime levels in an area is the percentage of the population that is black and Hispanic." Then, using single variable regression, they compared correlations by state including DC (see pages 11 and 12).
Wanting to replicate for verification and introduce a few other factors that conventional wisdom often asserts as having a causal relationship to crime, I took the latest numbers available (the Kaiser Foundation has a fabulous, user-friendly site for state-by-state comparisons for several factors) and looked at the relationship of violent crime (murder, non-negligent manslaughter, forcible rapes, robberies, and aggravated assaults) by state and the following factors (with correlations; "inverse" indicates an increase in the factor reduces violent crime; statistically significant unless otherwise stated):
% of population in poverty: .399
% of population with a bahelor's degree: .289 (inverse)
State gini coefficient: .627
% of population owning at least one gun: .060 (inverse, not statistically significant)
% of population with a high school diploma: .388 (inverse)
% of population unemployed: .309
% of population black or Hispanic: .800
Very little variance with what Amren came up with for the measures they used. But most telling are the results of a multivariate regression to determine the combined effects of the first six factors listed (all but the racial categorization). Surely entering all of these factors together will be more predictive than simply knowing what racial box residents check on their Census forms! Actually, they're not. Including all of them yields an r of .689. Thus, knowing how many people in a state are black and Hispanic reveals more about the amount of violent crime than does knowing the number of people in poverty, holding a bachelor's degree, having graduated from high school, owning a firearm, who are unemployed, and the level of income inequality combined.
When the percentage of the population that is black or Hispanic is included and each factor is controlled for by the other variables listed, in addition to the percentage of the population that is black or Hispanic (p-value of .00000109), only the percentage of the population that has completed high school retains statistically significance (p-value of .025), but interestingly becomes positively related to the incidence of violent crime. Racial composition remains just as strong a predictor of crime as it does when the other factors aren't included. Not surprinsingly, the r value (correlation) only increases to .836 with the addition of the other six factors.
As people of European ancestry continue to hemorrhage away their numerical dominance, the US will become an increasingly violent place (or one that has an ever-growing prison population, the seemingly most effective way to cut down on crime being to throw people in jail). The detrimental effects of a browner population will be partially offset by an increase in Asians who, despite suffering higher poverty rates than whites and being a numerically less powerful ethnic special interest group than blacks or Hispanics, are far less likely to commit violent crimes than any other racial group (only a quarter as likely as whites). Every one percent increase in population represented by Asians reduces the number of violent crimes per 100,000 people by 25, a per capita effect stronger than that of blacks, whites, or Hispanics.
What should realists do with this information? Reject the sea of crap about the differences in geographical locations that fails to take into account each location's racial and ethnic composition. Vociferously argue for an end to unfettered, largely Hispanic, illegal immigration and the instituting of a merit immigration system that reduces the number of legal immigrants to a couple hundred thousand annually while insuring that those accepted will increase the quality of life for the current US citizenry.
Paraenthetically, genuine liberals concerned with the perpetually increasing wealth disparities in the US can argue against open borders by pointing to the deleterious effect it has on the wages of the least skilled natives and the strong relationship between housing unaffordability and the proportion of a location's foreign-born population. To insulate themselves from the charges of Hispanophobia and other ad hominen that scare whites into self-immolation, they should point out the moderately strong relationship between crime and wealth inequality referenced above.