In all four cases, there is no significant empirical connection between changes in the crime rate and changes in the immigrant/population ratio.
And yet: "There is very little correlation between levels or changes in funding and crime rates, or between changes in police numbers and crime rates".
The National Academies of Sciences, Engineering, and Medicine concluded in 2005 that "no link between right-to-carry laws and changes in crime is apparent in the raw data".
Figure 4 Changes in crime and immigration.
Accordingly, the drop in crime may have been associate with changes in crime concentration across decades.
As Farrell (2013) observes, most of the crime drop hypotheses are crime generic, attributing changes in crime to changes in the number or motivation of offenders.
The different ways in which security measures work produce variations in expected changes in crime patterns associated with crime drops.
A discussion on equity and the crime drop requires examining the changes in crime incidence and victimisation divides in tandem.
Most researchers have used administrative crime panel data on an attempt to estimate the macro-causal impact of immigration on crime by relating changes in migration stocks to changes in crime rates.
However, it is possible that they are differentially correlated with changes in crime.
