It is possible to read in these case studies a lesson about the fate of modern liberalism. Liberals have been powerless in recent years to counter the argument that their policy prescriptions don’t work. A program that spends, say, an extra thousand dollars to educate inner-city kids gets cut by Congress because it doesn’t raise reading scores. But if reading problems are nonlinear the failure of the program doesn’t mean — as conservatives might argue — that spending extra money on inner-city kids is wasted. It may mean that we need to spend even more money on these kids so that we can hit their tipping point. Hence liberalism’s crisis. Can you imagine explaining the link between tipping points and big government to Newt Gingrich? Epidemic theory, George Galster says, “greatly complicates the execution of public policy. . . . You work, and you work, and you work, and if you haven’t quite reached the threshold you don’t seem to get any payoff. That’s a very tough situation to sustain politically.” After rereading paragraph #19 (see above), explain what the author is trying to express. What is the central point of this paragraph?