What's melting, exactly? Not the kids' apps, but the mom-and-pop stores. Derek's Coffee and Thompson's Corner Store would be considered start-ups. But a new Starbucks or Whole Foods is considered part of an existing franchise. So as chains have expanded by more than 50 percent since 1983—Walmart gobbles up smaller competition with a particularly greedy appetite—start-ups have perished, as Jordan Weissmann has explained. The demise of small new companies isn't limited to retail. Construction and manufacturing start-ups have collapsed by more than 60 percent in the last four decades. Here's the industry-by-industry die-off from Brookings data ("entry rate" is an industry's share of firms that one-year-old or younger):

So there are fewer new companies, and a lot more Dunkin Donuts. Why should you care? Because it's a sign that America has lost its edge? Because Big Government is killing entrepreneurship? Because McDonald's is gross? Not necessarily. Americans are still among the most productive workers in the world, countries with much "bigger" governments (by tax revenue, at least) have much higher rates of self-employment and small business formation, and McDonald's breakfast is objectively better than many small restaurants that don't know how to do proper hash browns.

One good reason to care about start-ups in America is that they tend to start ... in ... America. Going back to the late 1970s, as globalization started to accelerate, the majority of net job creation has come from new companies, rather than old firms, which are often expanding abroad. The vast majority of job creation at big multinational corporations—as much as 75 percent of new jobs—happens overseas, since other countries are growing considerably faster than our 2-percent rate.

One paradox of globalization is that it's localized employment. Since big companies off-shore much of their job growth (or replace what's left of it with software or smart hardware), the future of work in the U.S. will come from work that absolutely has to be here, like health care, education, and food services. Start-ups can be special for many reasons—they can challenge lumbering incumbents, they can create new demand for stuff, they can introduce more ideas—but from a big-picture macroeconomic standpoint, they're also special because they're here, and when they expand they tend to expand here. It's easy to make fun of Silicon Valley these days. But at least its companies have a California address.