Data in the Streets

November 2, 2014
Posted by Jay Livingston

I confess, I have little memory for books or articles on methods. I may have learned their content, but the specific documents and authors faded rapidly to gray.  And then there’s Unobtrusive Measures. It must have been Robert Rosenthal who assigned it. He was, after all, the man who forced social scientists to realize that they were unwittingly affecting the responses of their subjects and respondents, whether those subjects were people or lab rats.  The beauty of unobtrusive measures is that they eliminate that possibility. 

Now that states have started to legalize marijuana, one of the questions they must deal with is how to tax it. Untaxed, weed would be incredibly cheap. “A legal joint would cost (before tax) about what a tea-bag costs” (Mark Kleiman, here). Presumably, states want to tax weed so that the price is high enough to discourage abuse and raise money but not so high that it creates a black market in untaxed weed.

The same problem already occurs with cigarettes.

The above graph, from a study commissioned by the Tax Foundation, shows that as taxes increase, so does smuggling. (The Tax Foundation does not show the correlation coefficient, but it looks like it might be as high as 0.6, though without that dot in the upper right, surely New York, it might be more like 0.5.)

In a high-tax area like New York City, many of the cigarettes sold are smuggled in from other states. But how much is “many cigarettes,” and how can you find out? Most studies of smuggled and counterfeit cigarettes get their estimates by comparing sales figures with smoking rates. The trouble with that method is that rates of smoking come from surveys, and people may not accurately report how much they smoke.

That’s why I liked this study by Klaus von Lampe and colleagues.* They selected a sample of South Bronx census tracts and walked around, eyes down, scanning the sidewalks for discarded cigarette packs to see whether the pack had the proper tax stamps.

 All in all, they picked up 497; of those, 329 still had the cellophane wrapper that the stamp would be on.  If there was a tax stamp, they sent it the state to determine if it was counterfeit.

In the end, they estimate that only 20% of the cigarettes were fully legit with state and city taxes paid. About two-fifths had no tax stamp, another 15% had counterfeit stamps, and 18% had out-of-state stamps.

Unobtrusive measures solve one methodological problem, but they are not perfect. The trouble  here, and in many other cases, is the limited range.  Extending this research to the entire city let alone the fifty states would be a huge and costly undertaking.

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* Hat tip to Peter Moskos, who mentioned it on his Cop in the Hood blog.

Whose Bad Guess is More Bad? Difficult Comparisons

October 29, 2014
Jay Livingston

How to compare percentages that are very different? 

A recent Guardian/Ipsos poll asked people in fourteen wealthy nations to estimate certain demographics. What percent of the population of your country are immigrants? Muslim? Christian?

People overestimated the number of immigrants and Muslims, and underestimated the number of Christians. But the size of the error varied.  Here is the chart on immigration that the Guardian published (here).

Italy, the US, Belgium, and France are way off. The average guess was 18-23 percentage points higher than the true percentage.  People in Japan, South Korea, Sweden, and Australia were off by only 7-8 percentage points.

But is that a fair comparison? The underlying question is this: which country is better at estimating these demographics? Japan and South Korea have only 2% immigrants. People estimated that it was 10%, a difference of eight percentage points. But looked at another way, their estimate was five times the actual number. The US estimate was only 2½ times higher than the true number.

The Guardian ranks Hungary, Poland, and Canada together since they all have errors of 14 points. But I would say that Canada’s 35% vs. 21% is a better estimate than Hungary’s 16% vs. 2%.  Yet I do not know a statistic or statistical technique that factors in this difference and allows us to compare countries with very few immigrants and those with far more immigrants.* 

My brother suggested that the Guardian’s readers could get a better picture of the differences if the chart ordered the countries by the immigrant percentage rather than by the percentage-point gap.

This makes clearer that the 7-point overestimate in Sweden and Australia is a much different sort of error than the 8-point overestimate in South Korea and Japan. But I’m still uncertain as to the best way to make these comparisons.

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* Saying that I know of no such statistic is not saying much. Perhaps others who are more familiar with statistics will know how to solve this problem.

Shootings and Elephants

October 25, 2014
Posted by Jay Livingston

Why would an apparently happy kid shoot several classmates? That seems to be the question that’s getting the attention of the press and perhaps the public. “Struggling to Find Motive,” said one typical headline. That’s the way we think about school shootings these days.

It’s unlikely that any of the motives that turn up will be all that strange. Fryberg may have been upset by a racial comment someone had made the day before or by a break-up with a girl. He may have had other conflicts with other kids. Nothing unusual there.

But “why” is not the question that first occurs to me. What I always ask is how a 14-year old kid can get his hands on a .40 Beretta handgun (or whatever the weaponry in the shooting of the week* is).  For Fryberg it was easy. The pistol belonged to his father. Nothing strange there either. Thirty million homes in the US, maybe forty million, are stocked with guns.

Do European countries have school shootings like this? Surely kids in Europe get upset about break-ups; surely they must have conflicts with their classmates; and surely, some of them may become irrationally upset by these setbacks.  So surely there must have been school shootings in Europe too.

I went to Wikipedia and looked for school shootings since 1980 (here and here).  I eliminated shootings by adults (e.g., Lanza in Sandy Hook, Brevik in Norway). I also deleted in-school suicides even though these were done with guns and were terrifying to the other students. I’m sure my numbers are not perfectly accurate, and the population estimate in the graph below is based on current numbers; I didn’t bother to find an average over the last 35 years. Still the differences are so large that I’m sure they are not due to technical problems in the data.

Europe, with 500 million people, had 14 school shootings. The US, with fewer people (300 million), had nearly ten times that many.

Does the US have a much greater proportion of kids who are mentally unstable? Do our schools have more bullying? Are European kids more capable in dealing with conflicts? Are they more stable after break-ups? Do they spend less time with violent video games? Do their schools have more programs to identify and counsel the potentially violent?  I’m not familiar with the data on these, but I would guess that the answer is no and that our kids are no more screwed up than kids in Europe. Or if there are differences, they are not large enough to explain the difference in the body count.

No, the important difference seems to be the guns.  But guns have become the elephant in the room that nobody talks about. Even asking about access to guns seems unAmerican these days. Thanks to the successful efforts of the NRA and their representatives in government, guns have become a taken-for-granted part of the landscape. Asking how a 14-year old got a handgun is like asking how he got a bicycle to ride to school.

When the elephant’s presence is too massive not be noticed – for example, when the elephant kills several people – the elephant’s spokesmen rush in to tell us that “No, this is not the time to talk about the elephant.”  And so we talk about video games and psychological screening and parents and everything else, until the next multiple killing. But of course that too is not the time to talk about elephants.




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* In this 43rd week 2014, yesterday’s killing was the 39th school shooting in the US since January 1.  Most of those got little press coverage. Unless someone is actually killed, a shooting might not even get coverage in the local news.

Risk Managers Are Worried About Inequality

October 23, 2014
Posted by Jay Livingston

Who’s worrying about inequality? It’s not just the scraggly bunch that occupied Zucotti Park, and not just the lefty economists and sociologists hefting a copy of Capital in the Twenty-First Century. Professional Risk Managers’ International Association surveyed risk managers, and they too are uneasy about inequality.

The majority (62%) said that inequality poses a risk to the economy. Only 14% were like “What, me worry?”

I’m not sure what risk managers do, but I’m guessing  the profession does not draw many  socialists to its ranks. When you see this kind of concern coming from sources other than the usual suspects (I found this graph in a Wall Street Journal banking page – here), you begin to think that the wealth gap is more than just a moral issue about what is right and fair; it’s a threat to general economic well-being.