There are many reason why crime rates decline over a certain period of time. But the study suggests a provocative link between fewer illegal aliens roaming the streets and a falling crime rate.

A study by City.com reveals that the crime rate in Phoenix dropped dramatically after the city dropped its sanctuary city policies.

Breitbart:

"When we eliminated our sanctuary policy back in 2008, we saw crime, violent and stolen vehicles fall by 25 percent," former Phoenix police officer and Executive Director of the Arizona Police Association Levi Bolton told Fox News Channel's William La Jeunesse in an interview. "We saw a 20-year low crime rate. When we were allowed and had the discretion to contact our federal immigration partners, crime fell drastically." Lajeunesse reported data from City-Data.com revealing that from 2008 to 2009, the murder rate in Phoenix dropped by 27 percent. Other crimes fell as well. Auto thefts fell by 36 percent, robberies 23 percent, thefts by 19 percent, burglaries by 14 percent, and assaults by 13 percent, the report states. The rates fell again in 2010, but by smaller numbers. The overall crime index fell by 20 percent the first year after the city's policy change. Police chiefs around the country tout that sanctuary cities are safer than cities that actually turn criminal aliens over to immigration officials for removal from the country. "Police chiefs across the nation believe that enlisting local police to enforce immigration law is a bad idea," California Senate President Pro Tem Kevin De Leon (D) told reporters during a recent press conference "Having [Immigration and Customs Enforcement] pluck criminals out of jail and send them across the border or wherever they came only to come right back endangers our communities." The University of California, Riverside, disagrees. A 2016 study by the university revealed that "violent crime is slightly higher in sanctuary cities." It concluded there is not a "discernible difference in violent crime rates, rape, or property crime" across the 55 cities in their study, La Jeunesse reported.

Finding a direct, causal link between the crime rate and illegal alien criminals is difficult because there are so many factors besides illegals that must be considered, including incarceration rates, declining or increasing population, and even the amount of resources devoted to crime prevention.

Having said that, it's hard to escape the conclusion that turning illegals over to the feds has had a positive impact on reducing crime. I suppose it depends on your point of view. If you are disposed to reject any evidence that removing illegal aliens who commit additional crimes from the community could reduce the number of serious crimes, you can find plenty of ammunition to buttress your point of view.

But to do that, you have to ignore the totality of the evidence. Statistics from one city could be an outlier, so it will be interesting to examine statistics from other cities that have changed their policies.