The advantages of public markets for unicorns and their investors

THE public markets in America are much less crowded than they once were. Twenty years ago America was home to 8,000 listed domestic firms; now the total is close to 4,000. In 2016, 74 firms made their stockmarket debut, compared with 600 two decades ago. This winnowing is unwelcome. Merger activity, which reduces the number of listed firms, is damaging competition. Overregulation, which deters younger firms from floating, deprives ordinary investors of opportunities to benefit from America’s corporate successes.