Mark Zandi is chief economist of Moody's Analytics. The opinions expressed in this commentary are his own.

So it's time we talk about the next recession.

I believe that the next recession is coming into view — the summer of 2020, to be precise.

The best long-leading indicator of an oncoming recession is when the economy passes through full employment. Economists endlessly debate the definition of full employment, but most think a good benchmark is a 4.5% unemployment rate. This is the so-called full-employment unemployment rate or natural rate of unemployment.

When the actual unemployment rate falls below the natural rate, wage growth accelerates, squeezing businesses' profits and causing them to raise prices for their wares more quickly. The higher inflation prompts the Federal Reserve to tighten monetary policy, and long-term interest rates to rise. The economy eventually overheats.

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