Fortuna has also found that companies that buy back an unusually large percentage of their shares often deliver low ROI. Of the five companies that reduced share count the most via buybacks since 2011, four (Nordstrom, ­McDonald's, IBM, and media company Discovery Communications) subsequently generated subpar returns. The exception was defense contractor Northrop Grumman. It bought back some $11 billion of stock over the past five years, reducing share count by about 30%. But those moves accompanied a strategic streamlining in response to reduced defense spending. Northrop maintained double-digit profit margins over that span, even as its revenues fell—pleasing investors, who have doubled its stock price over the past three years.