Sociological theory has previously linked black urban decline to poverty,  loss of manufacturing jobs and racial segregation.

A new study in Social Forces claims another factor should be added into the dense cluster of black disadvantage – harsh immigration policies, which inadvertently flood low skill markets with Latino labor, displace blacks and, as a result, raise the rates of black murder.

Before the United States/Mexico border was militarized, Latino immigration was a two-way trip; immigrants, mainly from Central America, moved to the United States temporarily to finance a project in their home country. But in response to U.S. public pressure, border security was intensified. Tall fences were built, cameras installed and the border was patrolled relentlessly by well-armed guards.

As a result, Latino immigrants in the United States stopped returning home for fear that they could not repeat the trip. This increased the number of Latino workers in the United States competing for jobs in agriculture, manufacturing and construction. Blacks lost that competition in many cities, and where that occurred, murder rates went up.

"This is an unintended but significant result of immigration policies," said Louisiana State University's Edward Shihadeh, lead author on the project. "This is not a blame game. We do not advocate restricting the flow of Latino migrants in either direction. This is what triggered the flow of events in the first place. There is no reason to deprive this country of the rich contributions made by Latinos. Our study simply describes how immigration policy opened a new chapter in the history of the U.S. labor market and how that harmed black communities."

"Blacks and Latinos both feel singled out and put upon. But few will address these issues because they're politically explosive," said Shihadeh. "The public mood makes this subject a live wire."