Economists from Adam Smith on have written about the evils and dislocations that monopolies bring to an economy. What has been much less written about over the years, however, are the evils of monopsony.
In the interest of saving wear and tear on 300,000 dictionaries, let me hasten to offer a definition. A monopoly is any entity that effectively controls the supply of a commodity. A monopsony, on the other hand, controls the total demand for a commodity.
Obviously, monopsonies are much rarer than monopolies. The only one I ever enjoyed happened years ago when I was traveling in Greece. A photographer, quite unasked, snapped pictures of the members of a tour I was on, and the next morning, he went from table to table in the hotel dining room, offering eight-by-ten glossies at outrageous prices and doing a brisk business.