This economist wrote that the case for government intervention “cannot become more than a prima facie one” until agencies “intervene advantageously,” presaging public choice arguments. John Maynard Keynes argued against a work by this economist, whose title Theory of Unemployment is frictional or voluntary. A phenomenon named for this economist, in which consumption rises because deflation increases real wealth, is also called the “real balance effect.” The optimal value of a policy named for this economist occurs when marginal social cost intersects marginal social benefit. This Cambridge economist names a policy used to correct outcomes from water pollution (10[1])and carbon (10[1])emissions. For 10 points, name this economist whose namesake taxes mitigate negative externalities. ■END■ (0[1])