Is America turning into a nation of hamburger flippers from a nation of workers who make things, like machine tool operators? Answer: No, says economist Ed Yardeni, in light of the recent April jobs report. And that's good news. Payrolls rose by 244,000 in April, following gains of 221,000 and 235,000 the previous two months. Some have debated whether a quarter of the increase in private payrolls, 62,000 new jobs, came from McDonald’s (MCD) hiring more Big Mac flippers. McDonald's went on a hiring spree recently, but those numbers will likely affect the May jobs report. Still, food services and...