Why Stock Buybacks May Be Slowed or Shut by the Virus

The effort to shore up U.S. businesses battered by the coronavirus pandemic has brought new attention to the single biggest investment most big companies have made over the past decade: their own stock. The defenders of share buybacks say it’s often the most efficient use of capital. Critics say it has left firms vulnerable to the kind of shock the virus has produced. Either way, it’s been a vital support for equities — but one that will probably be sharply curtailed for a while, for both econo