U.S. railroad companies’ refusal to grant paid sick leave to their workers has exposed a startling vulnerability in the American economy: Rail staffing levels are not high enough to allow employees to take time off when they are ill. While Congress has intervened to block a strike, the underlying cause of the labor dispute — systemic understaffing — will persist. It’s the product of the companies’ years-long obsession with increasing efficiency and lowering costs, which has resulted in their slashing their payrolls by tens of thousands. And it’s yet another example of a misguided belief that is prevalent in other sectors, including manufacturing, health care (e.g., hospitals, nursing homes, pharmacies), and retailing.