He is a professor of economics at George Mason University,[4] a senior research fellow at the Mercatus Center, an adjunct scholar at the Cato Institute, and a former contributor to the Freakonomics blog.

It draws heavily from the Survey of Americans and Economists on the Economy in making the argument that voters have systematically biased beliefs about many important economic topics.

[21] In 2011, Caplan published his second book, titled Selfish Reasons to Have More Kids, arguing that people often work too hard in child-rearing, and as a result, they are scared of the idea of having children.

[31][32] Other writers have since said of someone that they can (or can't) "pass an ideological Turing test" if they are deemed to be capable (or incapable) of understanding and accurately stating an adversary's arguments.

Drawing on the economic concept of job market signaling and research in educational psychology, the book argues that much of higher education is very inefficient and has only a small effect in improving human capital, contrary to much of the conventional consensus in labor economics that Caplan claims takes the human capital theory for granted.

[35][36] Caplan and Saturday Morning Breakfast Cereal cartoonist Zach Weinersmith created the graphic non-fiction book Open Borders: the Science and Ethics of Immigration, which was released on October 29, 2019.

[40] Williamson said that the book was "fun to read" and well-presented but that Caplan did not address some obvious counterarguments against open borders and suggested that he oversimplified the issue.

Tyler Cowen wrote a reaction to the book, stating that his disagreement with Caplan is "that most of the inequity occurs upstream of labor markets, through the medium of culture.