With PolitiFact addendum at the end.
If you’ve heard about Marco Rubio saying we need more marriage to reduce poverty, you might wonder where his factoid came from.
The greatest tool to lift children and families from poverty is one that decreases the probability of child poverty by 82%. But it isn’t a government program. It’s called marriage.
According to the U.S. Census, the poverty rate for single parents with children in the United States in 2009 was 37.1 percent. The rate for married couples with children was 6.8 percent. Being raised in a married family reduced a child’s probability of living in poverty by about 82 percent.
That’s it! (37.1 – 6.8) / 37.1 = .82, so marriage reduces poverty 82%. You don’t get to be the “intellectual godfather of welfare reform” without knowing a thing of two about statistics.
By the same logic, he should have said, “The greatest tool for lifting children and families out of poverty is getting a job, which increases your income by $40,000 per year” — because 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.
Discussing why this is or isn’t wrong could be a nice methods class exercise.
PolitiFact evaluated the Rubio statement, and aside from a few insignificant quibbles determined it was true, so they gave it a rating of “Mostly True.” They wrote, in explanation:
We should note that some critics have taken issue with the implications of the statistic Rubio cited. Philip N. Cohen, a sociologist at the University of Maryland, wrote on his blog, “By the same logic, (Rubio) should have said, ‘The greatest tool for lifting children and families out of poverty is getting a job, which increases your income by $40,000 per year’ — because 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.”
Meanwhile, the liberal group Think Progress pointed to a blog post from a few days earlier by the Council on Contemporary Families, a group of academics that study family policy, that said a “nationally representative study of more than 7,000 women found that approximately 64 percent of the single mothers who married were divorced by the time they reached age 35-44. More importantly, single mothers who marry and later divorce are worse off economically than single mothers who never marry.”
These may be valid points. However, in his comments, Rubio did not suggest that government pursue any specific government policies to directly promote marriage. He also said that being a two-parent family “decreases the probability of child poverty,” which sounds to us like a mathematical analysis of the existing data, rather than a suggestion that changing policies to encourage marriage will actually reduce poverty that already exists.
For this reason, we are analyzing the mathematics that underlie his comment question, not the conclusions that can, or can’t, be drawn from the statistic.
It’s not about policy or math, though: the error is about causality. If we made a law that only rich people could get married, the Census data would give you a similar result. And by this reasoning PolitiFact would say it’s OK to claim marriage “decreases the probability of child poverty,” because the math is right. That’s not right.