New Delhi, March 12 -- POSITIVE THINKING can help people who are feeling down. Politicians, too, grasp that gloomy expectations can be self-fulfilling. In the late 1970s, as America grappled with an energy crisis and stagflation, President Jimmy Carter warned that the gravest danger was a "crisis of confidence" corroding public institutions and private enterprise. Decades later Abe Shinzo, Japan's longest-serving leader, argued that stagnation was sustained by a "deflationary mindset", and tried to jolt households and firms out of it. Xi Jinping, China's paramount ruler, has made promoting "positive energy" a national priority.

Today positive energy is in short supply. Pessimism has become widespread and persistent. In America consumer s...