Suppose that one scholar maintains that the average voter's belief about X is true, and another denies it. For their debate to make sense, both sides have to claim knowledge about (a) what the average voter believes, and (b) which belief is true. How can we get to the bottom of this sort of dispute?
It is fairly easy to figure out what the average voter believes. High-quality surveys abound. The hard thing is figuring out how to "grade" the beliefs of the average voter — to find a yardstick against which his beliefs can be measured.
The most straightforward is to compare voter beliefs to known fact. We can ask voters to tell us the fraction of the federal budget that goes to foreign aid, and compare their average answer to the actual number. Studies that use this approach find that the average voter has some truly bizarre beliefs. The National Survey of Public Knowledge of Welfare Reform and the Federal Budget finds, for example, that 41% of Americans believe that foreign aid is one of the two biggest areas in the federal budget — versus 14% for Social Security.
The main drawback of this approach is that many interesting questions are too complex to resolve with an almanac. But there is another mirror to hold up to public opinion. We can track down people who are unusually likely to know the right answer, see what they think, then check whether the public agrees. Who might these unusually-likely-to-know people be? The most obvious candidates are experts.
To see if the average voter's beliefs about the economic effects of immigration are right, for example, you can ask the general public and professional economists, and see if, on average, they agree. Is this an infallible test? No; experts have been wrong before. But it is hard to get around the strong presumption that if experts and laymen disagree, the experts are probably right, and the laymen are probably wrong. More importantly, if you have some specific reason to doubt the objectivity of the experts, you can control for it. If you think that economists' high income biases their beliefs, for example, you can check whether laymen and experts agree after statistically adjusting for income.
This was precisely the approach that I used to analyze the best available data set on economic beliefs, the Survey of Americans and Economists on the Economy. The overarching finding: Economists and the public hold radically different beliefs about the economy. Compared to the experts, laymen are much more skeptical of markets, especially international and labor markets, and much more pessimistic about the past, present, and future of the economy. When laymen see business conspiracies, economists see supply-and-demand. When laymen see ruinous competition from foreigners, economists see the wonder of comparative advantage. When laymen see dangerous downsizing, economists see wealth-enhancing reallocation of labor. When laymen see decline, economists see progress.