Major U.S. employers are starting to take a new approach to jobs: Hire less—or not at all. T. Rowe Price is slowing hiring. JetBlue is reducing nonessential hiring. Polaris, which makes off-road vehicles, has paused some hiring for now. And more than a dozen universities, from Harvard to Duke, have enacted hiring freezes. All the organizations, and many more, say bringing in fewer employees will help them cut costs and weather a turbulent moment. “We have instituted our recessionary playbook," Robert Mack, chief financial officer of Polaris, told investors last week, citing a downturn in its industry. A stop-start trade…