For decades, economist Walter E. Williams has been touting the benefits of free markets, arguing that they’re not only economically efficient, but also the best way to improve the lot of the poor. He returns to that line of argument in Race and Economics, a collection of essays that are connected only loosely — all they have in common is some relation to the two topics in the book’s title. Most of them simply reiterate points that Williams has made many times in his illustrious career: Occupational-licensing laws make it hard for people with low skill levels, a group that …