Alkahest my heroes have always died at the end

Presumably, most people have now heard that Arizona has passed a new law respecting immigration enforcement.  Reactions, as one might expect, are mixed depending on one’s thoughts on immigration, and more specifically, the potential for illegal immigration.  Mexico has issued a travel warning for its citizens, advising them not to visit the state.  Various AZ mayors have decried the law.  Some right wingers love it, while others hate it, and of course George Will is still an asshole.  And finally, even though the law doesn’t go into effect for another three months or so, we can already see what the future will be like for Hispanics in Arizona.

Honestly, I can’t believe that we’re talking about a state where you might expect law enforcement to request your papers.

I did have a few questions, including what exactly does the law require?  And how will it be enforced?  In a nutshell, the law:

Requires officials and agencies to reasonably attempt to determine the immigration status of a person involved in a lawful contact where reasonable suspicion exists regarding the immigration status of the person, except if the determination may hinder or obstruct an investigation.

Okay, so, how does one form a reasonable suspicion?  Well, good for Arizona, the law further:

Stipulates that a law enforcement official or agency cannot solely consider race, color or national origin when implementing these provisions, except as permitted by the U.S. or Arizona Constitution.

So, I don’t know what is permitted by the Arizona Constitution, maybe all of those forms of profiling, maybe none.  But one final question, given that the mayor of Phoenix doesn’t support the law, how do you guarantee that it gets enforce?  Well, a citizen can sue if there’s a policy that doesn’t support enforcement:

Allows a person who is a legal resident of this state to bring an action in superior court to challenge officials and agencies of the state, counties, cities, towns or other political subdivisions that adopt or implement a policy that limits or restricts the enforcement of federal immigration laws to less than the full extent permitted by federal law.

Requires the court to order any that a violating entity pays a civil penalty of at least $1,000 and not to exceed $5,000 for each day that the policy has remained in effect after it has been found to be violating these provisions.

A few thoughts:

1. It’s not clear to me how one forms a reasonable suspicion about the immigration status of the person, except given their ethnic background
2. It’s not clear to me that ethnic background is even restricted as a category for consideration in the law, based on Latinos being Caucasian and questions about what is permitted under Arizona’s constitution
3. Given #1 and #2 above, I don’t think people realize how ineffective ethnicity is in determining legal status

Fortunately, statistics gives us a good answer to #3.  For the following, let’s consider that L indicates Latino, and I represents illegal.

Bayes rule tells us that the probability of being illegal given that you are Latino [ Pr(I | L) ] is the probability of being illegal (the prior, Pr(I)) times the probability of being Latino given that you are Illegal (likelihood, Pr(L|I)) divided by the evidence or the probability of being illegal given Latino and given not Latino [Pr(L|I)*P(I) + Pr(L| not I)*Pr(not I)]

so, Pr(I|L) = Pr(L|I) * Pr(I) / (Pr(I|L) + Pr(I| not L))

We can quantify this somewhat, from StateMaster

The population of AZ = 5,939,292

Legal Hispanic/Latino population of AZ = 1,803,377

Estimated number of illegals in AZ = 283,000

If we assume that all illegals are Hispanic, then:

P(I) = 283,000 / 5,939,292 = .04765

P(L|I) = 1.0

P(L| not I) = 1,803,377 / 5,939,292 = .30364

So, the probability of being illegal given that you are Latino is:   .14147 or ~14%.  Which in my mind is no reason to form a suspicion.  Hell, more that 14% of the population are pot smokers, you wouldn’t want to give the police authority to stop and arrest everyone to find that subset who are.

CAVEATS AND NOTES

• The data above are from 2000 and may not be current; however, illegal immigration shows a strong economic correlation and the economy is down compared to the boom year of 2000, so the numbers are probably in the right ballpark
• I don’t believe that Pr(L  | I) = 1.0.  This says that all illegals are Latinos.  That’s bull.  There are plenty of Asian and European illegals.  Adjusting this probability down will significantly decrease Pr(I | L).  For example, assuming P(L|I) = 0.8 results in P(I|L) = ~.116.
• The above analysis assumes that Bayes’ law is true, but if it isn’t then we’re all seriously screwed.
• Finally, I would be uncomfortable with racial profiling even if Pr(I|L) > 0.5.  It’s just not America when the cops stop and ask you for your citizenship papers.  I can think of a few places where that did occur, but won’t risk the Godwin retraction by invoking them.

So, what to do?  I was challenged a few years ago as to my solution to the illegal immigrant “problem.”  My first response is that you are assuming it’s a problem.  After all, studies have shown that low-wage legal and illegal immigrants actually grow an economy.  Moreover, since many pay into Social Security and Medicare, without receiving benefits, that helps those programs.  OTOH, it’s not fair to have them pay in without receiving services; moreover, the social safety net should be expanded to help all those in our community.  So, in that sense illegal immigration is a problem.   However, the solution is straight forward.  Enforce current laws restricting a business’s ability to hire illegals.  Illegals come here due to the draw of jobs.  Businesses love ’em because they often work below minimum wage, and don’t complain about things like OSHA requirements.  Fine – regulate the businesses better and we’ll