When the rich get richer, they do not spend more—or at least in the right way to stimulate the economy. And low interest rates after the financial crisis benefited the rich disproportionately, keeping the economy sluggish and backfiring as a policy measure. Those are the primary lessons from Gary Stevenson’s The Trading Game, an economics course for our time masquerading as an updated mixture of Liar’s Poker and Good Will Hunting...