Monday, 7 November 2016

What would the electoral college have looked like in 2012 if illegal immigrants could vote?

According to Pew Research, the states with the largest illegal immigrant populations are as follows:

Of these states, Romney won Texas, Georgia, Arizona and North Carolina in the 2012 election––garnering him 103 electoral college votes. Would he have still won them if illegal immigrants could vote? 

Almost all illegal immigrants are Hispanics. 71% of Hispanics voted for Obama in 2012, while 27% voted for Romney. The Hispanic turnout rate was 48%. Therefore, the results in Texas, Georgia, Arizona and North Carolina would have been as follows if illegal immigrants could vote:

Romney would probably still have won all four of these states. However, his margins of victory would have been quite substantially reduced. 

Tuesday, 4 October 2016

How much does the pill increase the risk of depression?

A recent article in The Guardian claims that "The pill is linked to depression – and doctors can no longer ignore it". It does so on the basis of a new study published in JAMA Psychiatry, which tracked all women aged 15-34 in Denmark over a number of years, and measured (among other things) their use of oral contraceptives, and their use of anti-depressants. The study's headline results were that: 
a) women who used oral contraceptives had a 23% higher risk of using anti-depressants for the first time 
b) adolescent females who used oral contraceptives had an 80% higher risk of using anti-depressants for the first time 
The author of the Guardian article seems to regard these results as highly alarming. Yet there are several reasons not to be too consternated. 

First, from what I can tell, the JAMA Psych study was largely correlational, rather than causal: only age and year were controlled for in the main analyses. Second, the authors also measured women's diagnoses of depression, and––for that outcome––the increase in risk associated with oral contraceptive use was only ~10% for women overall (but it was still around 70% for adolescents). Third, and most importantly, the effect sizes do not appear to be very large. 

The crude incidence rate for women overall was ~1.7 per 100 person years. In other words, if 100 women who were not using oral contraceptives lived for 1 year, 1.7 of them would be expected to use anti-depressants for the first time during that year. The results above imply that this figure rises to 2.1 for women using oral contraceptives. The crude incidence rate for adolescents was ~0.9 per 100 person years. So if 100 adolescents who were not using oral contraceptives lived for 1 year, 0.9 of them would be expected to use anti-depressants for the first time during that year. The results above imply that this figure rises to 1.7 for adolescents using oral contraceptives. (The crude incidence rates for diagnoses of depression were much lower.) 

Sunday, 10 July 2016

Is county-level racial bias in police shootings unrelated to race-specific crime rates?

Yesterday, I suggested that the overrepresentation of blacks among the victims of police shootings may not be primarily attributable to racial animus on the parts of police officers. In response, a paper by Ross (2015; PLOS ONE), which claims the following, was brought to my attention:
There is no relationship between county-level racial bias in police shootings and crime rates (even race-specific crime rates), meaning that the racial bias observed in police shootings in this data set is not explainable as a response to local-level crime rates.
To his credit, Ross made his dataset publicly available (see in the Supporting Information), so I carried out a few analyses on it myself. 

The total number of victims in the dataset with known race is 647. There are 260 counties with at least one police shooting of a victim with known race (8% of total counties). 23% of counties have 100% black victims, 55% of counties have 100% white victims, and the remaining 23% have some mix of black and white victims. The mean percentage of victims who are black is 33%. Furthermore, 90% of counties have five or fewer victims, 80% have three or fewer, and 57% have exactly one victim; the mean number of victims per county is 2.5. 

The low number of victims per county seems to me to be a serious limitation of Ross's analysis. How can one reliably model an aggregate-level variable (such as the ratio of black to white victims, or the proportion of victims who are black) that, for most counties, is based on only one or two observations? 

I calculated the 95% confidence interval for the proportion of victims who are black in all 260 counties. (Thanks to Emil Kirkegaard for calculating confidence intervals for cases where p = 1 using the prop.test in R.) This confidence interval overlapped with p = .13 (the percentage of blacks in the general population) in 87% of counties. And when restricting the analysis to unarmed victims, the confidence interval for the proportion of victims who are black overlapped with p = .13 in 89% of counties. In other words, for >85% of counties, one cannot rule out that the true proportion of victims who are black is equal to the proportion of blacks in the general population.

The limitation of low numbers of cases per county was not lost on Ross. In the Methods section he notes that:
County-level police shooting rates are estimated using binomial probabilities, and a prior, estimated from the data, under hierarchical partial pooling. Hierarchical pooling allows information collected in other counties within the United States to partially inform the parameter estimates in a focal county, which improves out-of-sample predictive inference globally... Prior to the introduction of multi-level modeling methods, relative risk ratios at local levels were very hard to infer... The multi-level Bayesian methods used here, partially (rather than fully) pool information across counties, allowing for more stable estimates in relative risk ratios
Not being familiar with these methods myself, I am not in a particularly strong position to judge their efficacy. But it seems to me that Ross's dependent variable will have been subject to considerable measurement error. Therefore, I'm not sure he can really be confident that there is no relationship between racial bias in police shootings and race-specific crime rates at the county level. This is not to say that there is a relationship, but simply that the evidence Ross presents for there not being one may not be very compelling. I would interested to hear others' perspectives. (Stata .do file available upon request.)

Saturday, 9 July 2016

Does racial animus explain killings of black civilians by US police?

This post examines the distribution of victims of police shootings by race, and by sex. Data on individuals killed by police were taken from the Washington Post database for 2015 and 2016. According to these data, over the last two years, 27% of those killed by police were black, and 39% of those killed by police while unarmed were black. Insofar as blacks represent only 13% of the US population, this implies that blacks are overrepresented among the victims of police shootings.

However, blacks are––for whatever reason––also overrepresented among the perpetrators of violent crime. It is possible that blacks are more likely to be killed by police because they are more likely to get into violent confrontations with police, or because police officers practice statistical discrimination. The chart below shows, from left to right, the racial distribution of: the US population (taken from the US Census Bureau); those killed by police; those killed by police while unarmed; murder offenders (taken from the FBI); and alleged police killers (taken from the FBI––averaging over the last five years of available data was done to obviate sampling error). 

Blacks represent 13% of the US population, 27% of those killed by police, 39% of those killed by police while unarmed, 53% of murder offenders, and 39% of alleged police killers. These figures suggest that blacks may not be overrepresented among the victims of police shootings once involvement in murder or police killings is adjusted for. By way of comparison, consider the corresponding distributions by sex, which are shown in the chart below. Men are much more likely to be killed by police than women. But they are about as likely to be killed by police as one would expect on the basis of their involvement in murder or police killings. 

Given the highly sensitive nature of the subject matter, some caveats are in order. First, I am not arguing that blacks deserve to be killed more by police than members of other races. Rather, I am simply pointing out that the overrepresentation of blacks among the victims of police shootings may not be primarily attributable to racial animus on the parts of police officers. Second, I am not denying that there are cases of racially motivated violence against blacks by police officers. Such cases are of course deplorable. Third, I am not denying that there is a problem with police violence in the United States. The rate of police shootings in the US seems disproportionate even to the US's comparatively high homicide rate.

Finally, I am happy to send the dataset I have assembled to anyone who wants it. 

Sunday, 26 June 2016

Did more old people than young people vote Remain?

According to a YouGov poll on the day of the referendum, 75% of people in the 18-24 age group voted for Remain, compared to 39% in the 65+ age group. I was able to locate two different sources of estimated turnout by age group: a Sky Data poll, and an analysis of data from a Lord Ashcroft poll by Future Canon

According to the Sky Data poll, turnout in the 18-24 age group was 36%, whereas turnout in the 65+ age group was 83%. This implies that 0.75*0.36 = 27% of young people voted Remain, and that 0.39*0.83 = 32% of old people voted Remain. 

According to the analysis by Future Canon, turnout in the 18-24 age group was 32%, whereas turnout in the 65+ age group was 78%. This implies that 0.75*0.32 = 24% of young people voted Remain, and that 0.39*0.78 = 30% of old people voted Remain. 

Having said that, these turnout figures do seem a little implausible. Is it really true that only 32-36% of young people voted? If one instead relies on Ipsos MORI's figures for the last general election, then turnout in the 18-24 age group was 43%, while turnout in the 65+ age group was 78%. This implies that 0.75*0.43 = 32% of young people voted Remain, and that 0.39*0.78 = 30% of old people voted Remain.

Overall, it is not implausible that the proportion of old people who voted Remain is similar to (or even greater than) the proportion of young people who voted Remain. Of course, many more old people than young people voted Leave.

Tuesday, 21 June 2016

My email exchange with Michael Dougan

Dear Professor Dougan,

As someone leaning toward voting Leave in the upcoming referendum, I found the following lecture you gave on the EU quite compelling: 

The reason for my email is that I would like to ask you about an issue not dealt with in the video––which I personally see as the most important one in the debate––namely that we do not appear to face a choice between leaving and staying in the EU as it currently exists, but between leaving and staying in an EU which is moving toward further political integration. I am quite happy to acknowledge that our current membership of the EU is a net positive for the economy, or at the very least not a net negative. However, the real issue to me is not whether our current membership is a net positive for our economy, but whether our future membership will be a net positive for our society.

Is your view that a) the EU will not move toward further political integration in the future, or b) it will move toward further political integration in the future, and this will be good for the British people?

In this regard, I have written a blog post about why I believe a European federal state is not feasible in the near term, even though much deeper fiscal integration is required to make the Eurozone work:

Kind regards,

Noah Carl


Dear Noah

Thanks for your email. Without meaning any offence, the only people I ever hear talking about the EU becoming a federal (super)state are the people who hate the idea. No-one I know working in the field of the EU – and that is a very large number of people in all walks of life – ever thinks about it! And there are two reasons. First, Treaty changes – including of the sort that would be needed to “further integrate” the EU – require unanimous agreement by the 28 Member States followed by 28 national ratification processes. In the UK, that would almost certainly mean… another national referendum on the EU! After all, the European Union Act 2011 requires a national referendum in the UK for any future EU reform which would involve even the slightest increase in the competences of the EU at the expense of the UK. Secondly, the peoples of Europe clearly don’t want a federal superstate: can Leave name a single country that would support this (as opposed to some 1950s statements from a dead politician or the weird musings of some minor living one)?

Best wishes



Dear Michael,

Many thanks for getting back to me so quickly. No offence taken. However, I would make three points in response. 

First, many senior politicians in Europe seem to be in favour of a federal state, as evidenced by statements they have made (I have sources for all these quotes):

"We decided to arrive at a political union via an economic and currency union. We had the hope––and we still have it today––that the Euro will gradually bring about political union... Most member states are not yet fully prepared to accept the necessary constraints on national sovereignty. But trust me, the problem can be solved."
––Wolfgang Schäuble

"The internal market and the common currency demand joint co-ordinating action. This will require us to finally bury some erroneous ideas of national sovereignty... National sovereignty in foreign and security policy will soon prove itself to be a product of the imagination."
––Gerhard Schröder

"The Constitution is the capstone of a European Federal State."
––Guy Verhofstadt

"The EU Constitution is the birth certificate of the United States of Europe. The Constitution is not the end point of integration, but the framework for––as it says in the preamble––an ever closer union."
––Hans Martin Bury

"Of course there will be transfers of sovereignty. But would I be intelligent to draw the attention of public opinion to this fact?"
––Jean-Claude Juncker

"We need a political union, which means we must gradually cede powers to Europe and give Europe control... We cannot just stop because one or other doesn’t want to join in yet."
––Angela Merkel

Second, if a European federal state were not the ultimate end point, why does the EU have a motto, an anthem, a flag, an annual holiday, a mascot, and even a personification (the mythological figure Europa)?

Third, as I noted in the blog post I linked you to in my first email, much deeper fiscal integration is arguably needed to make the Eurozone work.

Kind regards,


Tuesday, 14 June 2016

Can the Eurozone survive?

The Eurozone faces a crisis of epic proportions. Unemployment in Spain stands at over 20%. Youth unemployment in Greece exceeds 50%. GDP per capita in Italy is back to where it was in 1996. This crisis––the crisis of the single currency––was not without forewarning. A number of prominent commentators predicted it some years in advance. One such commentator was the economist Martin Feldstein, who in a 1997 Journal of Economic Perspectives article noted:
My own judgement is that the net economic effect of a European Monetary Union would be negative. The standard of living of the typical European would be lower in the medium term and long term if EMU goes ahead than if Europe continues with its current economic policies…
Another such commentator was Baroness Thatcher, who in a 1992 interview with Forbes remarked:
Every single fixed exchange rate has cracked in the end. We’re all at different levels of development of our economies. Some countries simply couldn’t live up to a single currency. It would mean massive extra subsidies from the rest of us for them or massive movements of immigration from their countries into ours. Both would cause resentment and not produce harmonious development.
Arguably most prescient of all, however, was the Nobel Prize-winning economist Milton Friedman, who in a 1997 article for Project Syndicate wrote:
Europe’s common market exemplifies a situation that is unfavourable to a common currency. It is composed of separate nations, whose residents speak different languages, have different customs, and have far greater loyalty and attachment to their own country than to the common market or to the idea of “Europe”. Despite being a free trade area, goods move less freely than in the United States, and so does capital. 
The European Commission based in Brussels, indeed, spends a small fraction of the total spent by governments in the member countries. They, not the European Union’s bureaucracies, are the important political entities. Moreover, regulation of industrial and employment practices is more extensive than in the United States, and differs far more from country to country than from American state to American state. As a result, wages and prices in Europe are more rigid, and labour less mobile. In those circumstances, flexible exchange rates provide an extremely useful adjustment mechanism… 
The drive for the Euro has been motivated by politics not economics. The aim has been to link Germany and France so closely as to make a future European war impossible, and to set the stage for a federal United States of Europe. I believe that adoption of the Euro would have the opposite effect. It would exacerbate political tensions by converting divergent shocks that could have been readily accommodated by exchange rate changes into divisive political issues.
As the quotations above imply, in order to make the Eurozone work, much greater fiscal integration of Eurozone economies is required. Employment and industrial law will need to be harmonised still further; various tax and spending powers will need to be transferred to Brussels; and far higher levels of inter-state migration will need to be encouraged. For illustration, compare the EU to the United States––a rather more successful monetary union. Whereas the EU (of which the Eurozone comprises the larger part) accounts for only ~3% of spending in Europe, the US federal government accounts for ~60% of spending in America. Whereas rich EU countries such as the Netherlands make net contributions on the order of 0.4% of GDP, rich US states such as Connecticut run net fiscal balances (federal taxes paid minus federal spending received) on the order of 5% of GDP. And whereas just ~4% of people who were born and still reside in the EU live outside their country of birth, ~31% of people who were born and still reside in the US live outside their state of birth. 

Is wholesale fiscal integration of Eurozone economies achievable? Evidence from surveys and opinion polls suggest that it is very likely not.

First, despite the EU’s extensive efforts to cultivate a Pan-European identity, Europeans continue to identify more with their nation than with Europe as a whole. There is no European demos. In the 2014 wave of the Eurobarometer survey, respondents were asked to say whether they identified: with their country only; with their country first, then Europe; with Europe first, then their country; or with Europe only. The average proportion identifying with their country only or with their country first was >90%; in no country did less than 75% of people identify as such. And if we again turn our attention to the United States, we see a starkly different picture. Only a tiny fraction of Americans––around 7%––identify more with their state than with the United States itself. 

Second, when questioned specifically about taxation, social spending and employment law, most Europeans are decidedly sceptical about further centralisation. In the 2005 wave of the Eurobarometer survey (administered before the financial crisis), respondents were asked to state, for each of a number of policy areas, whether they believed decisions should be taken separately at the national level or jointly at the EU level. Only 39% supported joint decision-making on fighting unemployment; only 29% supported joint decision-making on health and social welfare; and only 25% supported joint decision-making for taxation. 

Third, there appears to be little appetite for softening the terms of the Greek bailout deal among citizens of the rich, creditor nations in Northern Europe. A YouGov poll conducted in July of 2015 found that 53% of Swedes, 61% of Germans, 64% of Danes and 74% of Finns were opposed to any renegotiation of Greece’s debt repayments. Moreover, sizable majorities in each of these countries––65% in Sweden, 59% in Germany, 70% in Denmark and 73% in Finland––blamed the Greek crisis squarely on successive Greek governments, rather than on either the troika (the EU, the IMF and the ECB) or on both Greek governments and the troika. The same poll found that 47% of Germans expressed a preference for Greece to leave the Eurozone. This percentage had risen to 59% in another YouGov poll carried out one month later. 

In conclusion: the Eurozone is currently embroiled in a crisis, a crisis which can only be overcome through much greater fiscal integration of Eurozone economies. Yet wholesale fiscal integration is not achievable in the near term. Europeans identify much more strongly with their nation than with Europe as a whole; they are largely opposed to the centralisation of taxation and social spending; and those living in the rich, creditor nations of Northern Europe show little appetite for fiscal transfers to their crisis-stricken counterparts in Greece. As Larry Elliot comments in The Guardian:
Brexit will remain a live issue unless the eurozone can sort itself out. That means either admitting that the euro has been a terrible mistake, or going the whole hog and integrating further, with a single banking system, a Europe-wide treasury, and a democratically elected finance minister with the power to raise money in Germany and spend it in Greece. This is not going to happen any time soon, and perhaps never.