Over the last two years, Cato has published three Immigration Research and Policy Briefs on illegal immigrant criminality. In each one, we found that illegal immigrants have lower criminal conviction rates in the state of Texas and lower nationwide incarceration rates relative to native-born Americans. Although nobody has criticized our methods or the data, we answer other criticisms that arise.

The best recent criticism is that illegal immigrant conviction rates are low because they are deported after they serve their sentences, which reduces their recidivism rates relative to native-born Americans who cannot be deported after being released from prison. Thus, the illegal immigrant incarceration or conviction rates are lower than those of native-born Americans because it is more difficult for them to recidivate as they would have to enter the country illegally again to do so. This has been a difficult criticism to address as data limitations are severe, but we attempted to do so after making some assumptions. We focused on comparing first-time criminal conviction rates.

We estimate that native-born Texans had a first-time criminal conviction rate of 683 per 100,000 natives in 2016. In the same year, we estimate that illegal immigrants had a first-time criminal conviction rate of 462 per 100,000 illegal immigrants – 32 percent below that of native-born Americans. Thus, about 36 percent of the gap that we observed in criminal conviction rates between illegal immigrants and native-born Americans can be explained by lower illegal immigrant recidivism that is likely due to their deportation.

This question could have been easily resolved by comparing the immigration statuses of first-time offenders. Of course, such data do not exist. Regardless, this is still an important question even if our estimate results from a back of the envelope estimate. You can judge for yourself how we came to this estimate. This is how we did it.

First, we used the Arizona state prison data from 2016 for those admitted to state prison that year. Of U.S. citizens sent to prison that year, 58 percent had previously been to prison at some point since 1984. The subpopulation of deportable non-citizens, which includes illegal immigrants but is not limited to them, had a recidivism rate of 47 percent – below those of U.S. citizens, but not that much below.

Second, we assumed that U.S. citizens are analogous to native-born Americans. This isn’t accurate, of course, but native-born Americans are 94 percent of Arizona’s citizen population so it is a reasonable back-of-the-envelope assumption.

Third, we assumed that the Arizona recidivism rates for prison by roughly approximated immigration statuses translate well to the Texas criminal conviction rates. This is our weakest assumption as not every criminal conviction results in incarceration and the Texas data on illegal immigrant and native-born convictions is more granular than the Arizona incarceration data.

Fourth, we subtracted the recidivism rates from 100 percent to estimate the first-time offender rate. Then we multiplied those numbers by the Texas criminal conviction rates by immigration status in 2016.

Our back-of-the-envelope estimate should not be the final word on this issue, but we cannot do better at this time due to the lack of specific data. Improved criminal justice and immigration data could easily answer these questions if such data are ever created or available. This estimate cannot be the final word on this topic. Regardless, our estimates do confirm the pattern of lower illegal immigrant criminality discovered elsewhere but the gap is narrowed.