The theory behind the so-called “Cadillac tax” on high-premium health plans is that people like Betty Diamond have too much health insurance, which causes them to get more medical care than they need. And if people like Diamond had thinner health care benefits, the theory continues, their bosses would pass the savings along in nice wage increases. But recent research studies argue such a tax will make employers cut benefits, make workers pay more or forgo health care, and put much of the savings back in management's pocket.