As a rule, private equity takes on the most troubled companies because turning them around offers the biggest profit opportunities. That's why private equity tends to generate more than its share of traumatic headlines. Look no further than Ripplewood Holdings' decision to put the maker of Twinkies into bankruptcy this week. It's the kind of decision that, were Ripplewood's principals ever to run for office, would get them savaged in an ad.

But guess what? Ripplewood also bought the company, Hostess Brands, out of bankruptcy three years ago, when it was called Interstate Bakeries. Ripplewood is just the latest manager to wrestle unsuccessfully with the company's fundamental problem, a unionized workforce in an industry where competitors aren't unionized.

Next time you're choosing a fattening indulgence in the checkout line, ask yourself if you're willing to pay extra so Twinkies and Wonder Bread (made by the same company) can arrive at the store on different trucks? So the driver can be excused from helping to unload? So the company can pay workers-comp costs way out of line the industry's? So a company with just 19,000 employees can administer 40 different pension plans?

We didn't think so.

But the best antidote to foolish thinking about job creation is the work of economists Steven J. Davis and John Haltiwanger. Their painstaking research has revealed a side of America's dynamism that isn't always pretty. Between 1977 and 2005, years roughly overlapping Mr. Romney's business career, some 15% of all jobs were destroyed every year, even as total jobs grew by an average of 2% a year. Job creation and destruction are both relentless, the authors showed in paper after paper. The small difference between the two is what we call prosperity.