To the degree the recent wild swings in the stock market are rooted in economic fundamentals, these are the fundamentals to fear: The already strong economy may overheat, inflation may spike, and the Federal Reserve may then raise interest rates more aggressively to try to combat that higher inflation. The kernel of evidence that supported those fears was a report Friday that average hourly earnings for American workers rose 2.9 percent over the 12 months ended in January, the highest since the economic expansion began nine years ago. It’s only a single data point, and an erratic one at that.