The study "Beauty and the Labor Market" by economists Daniel Hamermesh and Jeff Biddle (1994) uses survey data to examine the impact that appearance has on a person's earnings. Hamermesh and Biddle found that the "plainness penalty" is 9 percent and that the "beauty premium" is 5 percent after controlling for other variables, such as education and experience. In other words, a person with below-average looks tended to earn 9 percent less per hour, and an above-average person tended to earn 5 percent more per hour than an average-looking person.

about labor market and earning differences to explain the possible reason(s) of thisdifference in earnings?