This year, global growth is being brought to you by the government. Rocked by an avalanche of growth-sapping shocks, countries around the world are tearing up savings plans and rolling out large fiscal stimulus packages financed by bumper budget deficits. From slow-growing Europe to the U.S. and parts of Asia, where multitrillion-dollar investments in artificial intelligence are fueling demand, the spending spree is expected to boost economic growth and jobs in the near term. Global growth could accelerate to a 3% annual rate over the next six months as a result, according to JPMorgan...