… is from a December 1975 “Open Mind” interview  with Milton Friedman ; this quotation was the featured “Notable & Quotable” in yesterday’s edition of the Wall Street Journal :
One of the great mistakes is to judge policies and programs by their intentions rather than their results. We all know a famous road that is paved with good intentions. The people who go around talking about their soft heart…. I admire them for the softness of their heart, but unfortunately it very often extends to their head as well. Because the fact is that the programs that are labeled as being for the poor, for the needy, almost always have effects exactly the opposite of those which their well-intentioned sponsors intend them to have. . . .
Take the minimum-wage law. Its well-meaning sponsors—there are always in these cases two groups of sponsors, there are the well-meaning sponsors, and there are the special interests, who are using the well-meaning sponsors as frontmen. You almost always, when you have bad programs, have an unholy coalition of the do-gooders on the one hand, and the special interests. The minimum-wage law is as clear a case as you could want. The special interests are of course the trade unions. The monopolistic craft trade unions in particular. The do-gooders believe that by passing a law saying that nobody shall get less than two dollars an hour, or $2.50 an hour, or whatever the minimum wage is, you are helping poor people who need the money. You are doing nothing of the kind. What you are doing is to assure that people whose skills are not sufficient to justify that kind of a wage will be unemployed. It is no accident that the teenage unemployment rate—the unemployment rate among teenagers in this country—is over twice as high as the overall unemployment rate.