I've gotten into two arguments with people who insist that right-wing economics is defined as free market, and left-wing economics is defined as interventionist. I disagreed, and naturally long arguments ensued.

My initial position was that the terms are relative concepts that are historically mutable: they are a function of what utility function you're using, and whose utility you're maximizing. I even took (and still take) the position that free trade can be a left-wing economic position, so long as the reason for the free trade policy is to achieve income redistribution in poorer countries.

My position was changed slightly when Nate pointed out that the historical basis for the terms left/right originated during the French Revolution, when the aristocrats would sit on the right and the commoners would sit on the left. During this period, "right-wing economics" was actually synonymous with feudalism, and laissez-faire was a left-wing economics position. Over time laissez-faire has drifted to the right and pushed feudalism who knows where.

This made me think a little more, so I amend my definition now to state that right-wing economics is defined as economic policies that maximize the utility of the stronger property owners and maintain their purchasing power, whereas left-wing economics are economic policies that maximize utility for all individuals as a whole. A possibly current-day instantiation of this definition could be that right-wing economics favor pareto-optimal results, while left-wing economics favor globally optimal results. Note that the two are not necessarily mutually exclusive, though in practice they frequently are, i.e. I get to keep my paradoxical assertion that free trade can be both a left and right wing policy, even simultaneously :).

This seems to be a historically neutral definition that encompasses present and past notions of left/right-wing economic policies, though it relies heavily on 'utility' fudge factor.