But this is anything but a don't-worry-be-happy column (I tend not to write a lot of those). It's a warning to recession watchers and, more so, to policymakers: Worry less about when the next recession is coming and worry a lot more about what we're going to do about it. Economists can't tell you when the next downturn is coming, but a lot of the current chatter is because of the current expansion entering its 10th year (it started in June 2009), which ranks it among the longest. Expansions don't die of old age: They're murdered by bubbles, central-bank mistakes or some unforeseen shock to the economy's supply (e.g., energy price spike, credit disruption) and/or demand slide (e.g., income/wealth losses). Also, trade wars.