an arbitrary power rating used, for example, in the analysis of statistical data to compare engines, machines, and other equipment of different powers in order to depict them as a given number of machines having the same power rating. Thus, data on a tractor fleet in the USSR are sometimes converted into arbitrary units of 15-hp tractors (1 hp = 0.736 kilowatt), that is, 15 hp at the drawbar is taken to be the equivalent power. A tractor that develops 75 hp at the drawbar, then, is equivalent to five tractors of 15 hp each.