The promise and peril of CVS buying Aetna

A few days ago, the pharmacy retailer CVS announced it would purchase health insurer Aetna for a cool $69 billion. The deal is one of the largest of 2017, and would create a health-care behemoth. Supporters of the deal — including, needless to say, the CEOs of both companies — argue it will deliver efficiencies, better service, and lower prices for customers. Critics worry it will drive even more consolidation in a health industry already dominated by giants, and leave everyone else worse...