The big puzzle in economics today: why is the economy growing so slowly?

Theory 1: We’re running out of innovations
Theory 2: There’s too little spending
Theory 3: Bad corporate governance is causing companies to under-invest
Theory 4: The economy is weighed down with debt
Theory 5: Excessive regulation is holding back growth
Theory 6: There’s too much housing regulation in big cities
Theory 7: The economy is becoming dominated by big, incumbent companies
Theory 8: A slow-growing, aging population is hurting growth