Tech giants’ market dominance could be more troublesome than any antitrust threats seen in U.S. history, and federal regulators have been slow to react to it, Nobel prize winning economist Joseph Stiglitz said

“Google and Facebook represent a more serious threat than Standard Oil did,” the former World Bank chief economist said, referring to the oil giant that gave birth to the antitrust law in the U.S. in the early 1900s.

“Some changes in technology made it apparent that there are very big enterprises that have large amounts of market power and represent a larger threat to competition than the...