Since 2009, the US unemployment rate has fallen from 10 percent to 4¼ percent, underpinned by steady job gains. Yet despite this employment strength, growth in output and wages has been disappointing. Many other countries have seen even worse economic performance. Are there policy changes that could help kick-start higher growth? John Fernald, whom The Wall Street Journal touts as the Federal Reserve’s “point man on productivity,” explores the possibilities with Austan Goolsbee, Chicago Booth professor and former chairman of President Obama’s Council of Economic Advisors.