Monday, July 25, 2011

When all of your studies are ecological

Consider this example:

By contrast, in England during the same period, the nobility and gentry didn’t conspire with the crown to exempt themselves from taxation. Instead, thanks to a number of factors—greater social solidarity, a keener sense of foreign threats, reforms that made the government itself less corrupt, and the principle of taxation only with the consent of Parliament—the wealthy of England willingly accepted higher taxes on themselves. As a result, government spending in England rose from 11 percent of GDP in the late seventeenth century to 30 percent during some years in the eighteenth century. That’s higher than U.S. federal spending today. These higher taxes on the wealthy in England, Fukuyama notes, “did not, needless to say, stifle the capitalist revolution.”

This is a persistent problem in the evaluation of programs: how do you determine the direction of causality in an ecological study? Did England become wealthy and thus feel free to raise taxes or did raising taxes allow England to prosper and become wealthy? The same issue arises with debating points made closer in time:

The idea that the economy will suffer if we modestly raise taxes on upper-income Americans is belied by recent history: we increased tax rates on the rich in 1993 and the economy created more than twenty-two million jobs; we cut them in 2001 and the economy created fewer than seven million jobs.

But it is clear that there were a lot of confounding variables between the two time periods. Still, it is interesting that most people seem to immediately see a link between raising taxes and lower economic growth. Why are we so sure about this link, given the weak relation seen historically?

It's a really challenging problem and, worst of all, one that data can't really help us with.

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