The proposed rule to eliminate drug rebates could take away plans’ power to lower drug prices, would not lower taxpayer spending on drugs, and the one problem it might alleviate, artificially high list prices, is likely already partially eased by mergers between insurers and pharmacy benefit managers, according to a former chief economist at the Justice Department’s antitrust agency. Yale University economics professor Fiona Scott-Morton said the better solution is to make drug companies pay insurers directly, instead of letting...