Who is better informed about the policy choices facing the country—liberals, conservatives or libertarians? According to a Zogby International survey that I write about in the May issue of Econ Journal Watch, the answer is unequivocal: The left flunks Econ 101.

Zogby researcher Zeljka Buturovic and I considered the 4,835 respondents' (all American adults) answers to eight survey questions about basic economics. We also asked the respondents about their political leanings: progressive/very liberal; liberal; moderate; conservative; very conservative; and libertarian.

Rather than focusing on whether respondents answered a question correctly, we instead looked at whether they answered incorrectly. A response was counted as incorrect only if it was flatly unenlightened.

Consider one of the economic propositions in the December 2008 poll: "Restrictions on housing development make housing less affordable." People were asked if they: 1) strongly agree; 2) somewhat agree; 3) somewhat disagree; 4) strongly disagree; 5) are not sure.

Basic economics acknowledges that whatever redeeming features a restriction may have, it increases the cost of production and exchange, making goods and services less affordable. There may be exceptions to the general case, but they would be atypical.

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Therefore, we counted as incorrect responses of "somewhat disagree" and "strongly disagree." This treatment gives leeway for those who think the question is ambiguous or half right and half wrong. They would likely answer "not sure," which we do not count as incorrect.

In this case, percentage of conservatives answering incorrectly was 22.3%, very conservatives 17.6% and libertarians 15.7%. But the percentage of progressive/very liberals answering incorrectly was 67.6% and liberals 60.1%. The pattern was not an anomaly.

The other questions were: 1) Mandatory licensing of professional services increases the prices of those services (unenlightened answer: disagree). 2) Overall, the standard of living is higher today than it was 30 years ago (unenlightened answer: disagree). 3) Rent control leads to housing shortages (unenlightened answer: disagree). 4) A company with the largest market share is a monopoly (unenlightened answer: agree). 5) Third World workers working for American companies overseas are being exploited (unenlightened answer: agree). 6) Free trade leads to unemployment (unenlightened answer: agree). 7) Minimum wage laws raise unemployment (unenlightened answer: disagree).

How did the six ideological groups do overall? Here they are, best to worst, with an average number of incorrect responses from 0 to 8: Very conservative, 1.30; Libertarian, 1.38; Conservative, 1.67; Moderate, 3.67; Liberal, 4.69; Progressive/very liberal, 5.26.

Americans in the first three categories do reasonably well. But the left has trouble squaring economic thinking with their political psychology, morals and aesthetics.

To be sure, none of the eight questions specifically challenge the political sensibilities of conservatives and libertarians. Still, not all of the eight questions are tied directly to left-wing concerns about inequality and redistribution. In particular, the questions about mandatory licensing, the standard of living, the definition of monopoly, and free trade do not specifically challenge leftist sensibilities.

Yet on every question the left did much worse. On the monopoly question, the portion of progressive/very liberals answering incorrectly (31%) was more than twice that of conservatives (13%) and more than four times that of libertarians (7%). On the question about living standards, the portion of progressive/very liberals answering incorrectly (61%) was more than four times that of conservatives (13%) and almost three times that of libertarians (21%).

The survey also asked about party affiliation. Those responding Democratic averaged 4.59 incorrect answers. Republicans averaged 1.61 incorrect, and Libertarians 1.26 incorrect.

Adam Smith described political economy as "a branch of the science of a statesman or legislator." Governmental power joined with wrongheadedness is something terrible, but all too common. Realizing that many of our leaders and their constituents are economically unenlightened sheds light on the troubles that surround us.

Mr. Klein is a professor of economics at George Mason University. This op-ed is based on an article published in the May 2010 issue of the journal he edits, Econ Journal Watch, a project sponsored by the American Institute for Economic Research. The article is at: http://econjwatch.org/articles/economic-enlightenment-in-relation-to-college-going-ideology-and-other-variables-a-zogby-survey-of-americans