Correlation and Causation: Marriage, Poverty, and Teeth

January 15, 2014
Posted by Jay Livingston

Is dentistry destiny?

A couple of days ago, I commented (here) on the idea that marriage was the solution to poverty.  Or as the Heritage Foundation (and Sen. Rubio) put it,

Being raised in a married family reduced  child’s probability of living in poverty by about 82 percent.

The evidence for this assertion was a comparison of two-parent and single-parent families. Sure enough, a higher percent of single-parent families were poor. That was enough for PolitiFact to give Rubio a “Mostly True.” And now The Wall Street Journal has given Bush’s press secretary Ari Fleischer space to repeat this idea (“How to Fight Income Inequality: Get Married” - here).

Rubio, Heritage, Fleischer, and PolitiFact are committing a fallacy most undergraduates would see through in two seconds – mistaking correlation for causation. 

Here’s an analogy that comes via the Christian Science Monitor (here – it first appeared in October, but I discovered only yesterday):

“What is your social class? Take our quiz to find out!”

The quiz has thirty items, including this one

16. Have you visited a dentist in the past year?

A “Yes” answer counted towards the upper end of the social class scale. 

people with more than a high school education were twice as likely to have visited the dentist in the past year. Those living below the poverty line or without a high school education were also twice as likely to be edentulous, or toothless.

Or as Heritage-Rubio would put it, “Visiting the dentist once a year reduced a person’s probability of being poor by 50%.” 

Using the same conservative perspective, we can easily see the logic of the dentistry-poverty connection and its implication for policy.  People with bad teeth or no teeth wind up with bad jobs or no jobs. They are not attractive as potential employees. Because of their poor personal decisions regarding dental care, they suffer economically. If only they would visit the dentist annually, they would almost certainly rise from poverty. Needless to say, the government should not do anything directly to alleviate their poverty or dental care.  These are matters of personal virtue, and the government’s role should be only to exhort them to visit the dentist regularly.

That almost sounds reasonable. But the reverse causation is so much more likely. It’s not that having bad teeth causes poverty. It’s that taking yourself and your kids to the dentist regularly costs money – something poor people don’t have a lot of.

The dentistry-marriage analogy isn’t perfect, but it does illustrate the fallacy of assuming causation. It also points to something in the real world. The correlation between single parenthood and poverty is not automatic. It depends on government policies. In countries that provide low-cost childcare, medical care, and other benefits and services, single parents and their children will not suffer economically as they might under more punitive policies. Many countries have seen large increases in unwed parenthood – much greater than in the US – and their rates of single parenthood are greater.  (The graph is part of this CDC report.)

(Click on the chart for a larger view.)

But how are children in these countries faring?  The comparison of poverty rates shows a negative correlation – the higher the rate of unwed parenthood, the lower the rate of child poverty.*

(Child poverty data are from this OECD report.)

The question is not whether marriage and regular dental check-ups and other matters of personal virtue enhance economic prospects for parents and their children.**  The question is what governments should do for children who made the mistake of choosing parents who were not financially well-off, educated, healthy, and virtuous. 
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* The OECD measure of poverty is relative rather than absolute – the percentage of children in families with incomes less than 50% of the national median.  The measure could more accurately be termed a measure of inequality. However, in surveys in the US, when people are asked what they think the poverty line should be – i.e., what’s the minimum amount a family around here needs to just get by – the answer is usually a number that is about 50-55% of the median income.  So the OECD number does reflect widely-held ideas about poverty.

** The Oklahoma Marriage Initiative consisted of “federally-funded relationship skills training programs to promote marriage among unmarried parents.”   Philip Cohen at the Family Inequality blog outsourced the analysis of the Intiative to Kristi Williams, who writes (here) of these programs: “The conclusion: They have failed spectacularly.”

Location, Location, Location

January 14, 2014
Posted by Jay Livingston

The chemical spill in West Virginia should be a much more important story than Chris Christie and the George Washington Bridge. But it’s the Bridge that’s getting far more attention in the media. 

Anne Marie Cox has a good piece in the Guardian (here) about “how it came to be that Bridgegate continues to attract punditry while West Virginia only generates the kind of sympathetic-if-distant coverage we usually grant far-off and not too devastating natural disasters.”

In West Virginia, there are 300,000 people without useable water, and an unknown number who may fall ill because the warning to avoid the tainted supply came seven hours after the leak was discovered – and perhaps weeks after it happened. (Neighbors of the plant have told reporters they detected the chemical’s odor in December.)

Surely, that’s more important than four days of traffic jams, which, truth be told, are hardly a strange and new horror for New York and New Jersey drivers.

Cox has several explanations for the disproportionate weight given to the Christie story. Not only might Christie be president in a couple of years, but he’s known. He’s a political celebrity.* And for some reason, stories about the personal deeds and misdeeds of celebrities are newsworthy. Apparently we prefer a story about personalities rather than about policy (especially policy that involves science, especially environmental science). 

Cox lists other reasons, but the one I think is most telling is geography.**

It is taking place in the literal backyard of most national political reporters. It has very little to do with policy, or numbers, or science.

In the old days – with no satellite transmission, with no Internet –  stories from New York, Washington, and perhaps a few other places dominated the news because that’s where the news business was located. Stories from other places were more expensive to produce and transmit.  Film would have to be flown from the hinterlands to production studios in New York. 

Today, remote stories do not run up costs. And in many ways the chemical spill should make for better news – the visuals are potential more striking, the potential interviews with the plain folks who are affected, the corporate baddies (it doesn’t get much better than “Freedom Industries”), the political influence, etc.

But it’s not just the cost. The sophisticated, cosmopolitan people who bring us the news turn out to be just as provincial in their own way as are the rubes they tacitly disdain.  If the 4-methylcyclohexane-methanol had been polluting the Hudson or the Potomac, it would have been a national story.  As it is, the unstated message in the media coverage is, “Forget it; it’s only West Virginia.”

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* Christie’s celebrity status is not an accident. One of the nuggets that the investigation has unearthed is that in choosing an ad campaign for the state to show its miraculous post-Sandy recovery, Christie chose a $4.7 million ad campaign over one that cost about half that much.  The pricier PR job Christie chose gave much greater prominence to Christie himself.

** Social scientists and media experts who know more than I do about how news is made must have written about this, but I have not come across any posts on these two stories.

Get a Spouse (sha-na-na-na. . . )

January 11, 2014
Posted by Jay Livingston

A bumper sticker I used to occasionally see said, “I fight poverty. I work.”

In this fiftieth anniversary of the War on Poverty, we should remember the difference between individual solutions to individual problems and societal or governmental solutions to social problems.  Yes, you’re less likely to be poor if you have a job. But exhorting the unemployed to go out and get a job is unlikely to have much effect on overall rates of poverty. 

The same can be said of marriage. In a recent speech, Sen. Marco Rubio offered the conservative approach to poverty.  The Rubio bumper sticker would say, “I fight poverty. I have a spouse.”  Here’s what he said:

 the greatest tool to lift people, to lift children and families from poverty, is one that decreases the probability of child poverty by 82 percent. But it isn't a government program. It's called marriage.

His evidence was drawn from a Heritage Foundation paper by Robert Rector.  Rector used Census data showing that poverty rates among single-parent families were much higher than among two-parent families – 37.1% vs. 6.8%.  “Being raised in a married family reduced child’s probability of living in poverty by about 82 percent.”

As Philip Cohen (here) pointed out, the same logic applies even more so to employment.

The median weekly earnings of full-time, year-round workers is $771 per week, which is $40,000 per year more than people with no jobs earn.

Philip apparently thought that this analogy would make the fallacy of the Rubio-Rector claim obvious, for he didn’t bother to spell it out. The point is that singling out marriage or employment as a cause ignores all the reasons why people don’t have jobs or spouses. It also implies that a job is a job and a spouse is a spouse, and that there is no difference between those of the middle-class and those of the poor.  (Philip should have spelled out the obvious. These logical problems did not bother PolitiFact , which rated Rubio’s claim as “mostly true.”)


According to Rubio, Rector, and PolitiFact, if all poor women with children got married, the child-poverty rate in the US would decrease by 82%.  Or at the individual level, if a poor single woman got married, her children would be nearly certain (93.2% likely) to be un-poor.

To illustrate the society-wide impact of marriage on poverty, Rubio-Rector look at the increase in out-of-wedlock births.  Here is a graph from Rector’s article.

The rate rises from about 7% in 1959 to 40-41% today.  If Rubio is right, rates of child poverty should have risen steadily right along with this increase (almost invariably  referred to as “the alarming” increase) in out-of-wedlock births.  The graph below shows poverty rates for families with children under 18.

Both show a large decrease in poverty in the first decade or so of the War on Poverty – between 1959 and 1974, the rate for all families was cut in half.  Since then the rate has remained between 9% and 12%.  The line for unmarried mothers shows something else that Rubio and Rector ignore: the effects of forces that individuals have no power over, things like the overall economy.  In the good years of 1990s, the chance that a single mother would be below the poverty line fell from nearly half (47%) to one-third.  Her marital status did not change, but her chances of being in poverty did.  The number of families in poverty fell from 6.7 million to 5.1 million – despite the increase in population and despite the increase in percentage of children born out of wedlock. There were more single mothers, but fewer of them were in poverty.

Addendum, January 12:  The title of this post refers to the classic oldie “Get a Job” (Silhouettes, 1957). The final lines of that song could, with only some slight editing, apply to Sen. Rubio and his colleagues:

In the Senate and the House
I hear the right-wing mouths,
Preachin’ and a cryin’
Tell me that I’m lyin’
’Bout a spouse
That I never could find.
(Sha-na-na-na, sha-na-na-na-na.)

Negative to Positive

January 7, 2014
Posted by Jay Livingston

Orwell disliked the “not un-” formation because it tried to make the banal sound profound. It’s a not unjustifiable complaint, and when Orwell says that, I couldn’t fail to disagree with him less.

I, too, try to avoid the “not un-” construction.  I’m not worried about being nailed for trying to pass off my banality as profundity. I just want to avoid double negatives. That sentence in the above paragraph has four negatives - couldn’t, fail, disagree, less – and  I’m still not sure whether it means I agree with Orwell or disagree with him. The thicker the multiple negatives, the harder it is for the reader to grope through them to the meaning of the sentence.

Even the writer can stumble. I read a recent blog post on how FDA regulations make it difficult for food companies to label their foods “Not Genetically Modified.” It linked to a WaPo story with this example:

[The FDA] told the maker of Spectrum Canola Oil that it could not use a label that included a red circle with a line through it and the words “GMO,” saying the symbol suggested that there was something wrong with genetically engineered food.

Here is what the comment* said:

it would be nice to buy products that were labeled GMO-free. I can’t buy them – not because there’s no demand for them, not because no manufacturers are unwilling to sell me products so labeled, but because the GMO industry has managed to change the rules to make that transaction impossible.

“Not because no manufacturers are unwilling to sell . . . ”  takes us into triple-negative territory. Even the person who wrote it must have been confused.  A half-hour later, the writer corrected the second part: “not because no manufacturers are WILLING. . . .” 

As an exercise in the power of positive thinking, I tried converting the negatives into affirmatives.

I can’t buy them, but why not?  The demand is there. The manufacturers are willing to sell me products so labeled. But the GMO  industry has managed to change the rules to make that transaction impossible.

It may sound less profound, but I think it’s clearer.

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* I use this example only because it happened to be close at hand.  It’s a casual comment, probably written in haste and not proofread. But I’ve run across the same kind of writing in more formal venues. 

(An earlier post on a more common version of this – “cannot be underestimated” – is here .)