Thursday, September 23, 2010

Value of College Degree Is Growing, Study Says

New York Times article "Value of College Degree Is Growing, Study Says" (September 21st, 2010) gets the correlation/causation distinction correct. However, it doesn't give the clear causal reasons why better educated and wealthier people eat more healthily and exercise more: while people often face the same price of an activity, they often face different shadow prices, the relevant price for making decisions.
The report, first issued in 2004 and updated in 2007, also described social benefits: those with a bachelor’s degree, it said, are more likely to volunteer, vote, exercise and have health insurance and pensions. They are also less likely to smoke, be obese or have low-birth-weight babies. It did not assert that a college education, by itself, was responsible for all those differences.

'Correlation is not the same as causation,' Ms. Baum said. 'But that said, the people who have done careful statistical analyses, controlling for demographic characteristics like income and family background, have overwhelmingly concluded that there’s some causation here, that some things that happen to you in college, for example, would make you more likely to adopt healthier behavior.'

Better educated and wealthier people have more incentive to live longer because their time is worth more. Take Kevin Murphy's shadow price of a cheeseburger example (briefly mentioned at the end of this interview). Eating unhealthy cheeseburgers shortens your life, but you gain happiness from them. The time of a low-wage person should be valued by that low-wage person as their wage (or outside wage, if the two are only approximately equal). While state-dependent utility disclaimers apply, the thrust of our argument will be robust to secondary and tertiary corrections.

Let us imagine that the time a rich person is willing to give up for an extra hour of his life is $200, but a poor person is only willing to give up $100. Then if a cheeseburger takes an hour off of an individual's life (for instance), then the true cost to a rich person is $204, while the cost to a poor person is $104. The shadow prices the two individuals face are different. Unhealthy decisions cost rich people more because they value their lives more.

When people decide to become educated, they induce themselves to have different marginal utilities and therefore make different decisions due to facing different shadow prices--a cheeseburger is more expensive for a rich person.

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