Are prices really plummeting? If you watch the official government gauge of prices in the economy, you would think so. Between March and April, the Consumer Price Index (CPI) dropped by 0.8 percent―that’s a decline of 9.1 percent at an annual rate! Even if we exclude food and energy, prices still fell at half that rate. And, both price measures already had begun to fall the previous month. Is this the new trend? Are we in the midst of a deflation? The short answer is no.

The pandemic is an enormous shock to both supply and demand (see our earlier post). The productive capacity of the economy is lower both now (with the lockdown) and in the medium term (with the need to make economic activity biologically safer). Similarly, demand is lower both temporarily while people stay at home and in the longer term as the propensity to save rises to enable people to pay off elevated debts and build precautionary buffers. Determining which of these shifts prevails is essential for policymakers. If the demand contraction dominates, then trend inflation will fall and policymakers will need to implement further expansionary policies. Conversely, if trend inflation rises (implying that the supply constraints prevail), then policymakers will eventually need to introduce restraint.

In this post, we discuss the difficulties of measuring inflation during a pandemic—when demand and supply both shift dramatically. Our conclusion is that some indices provide better high-frequency signals of the trend. Unsurprisingly, headline measures of inflation are especially poor. Yet, traditional measures of “core inflation” that exclude food and energy may be equally bad. Instead, we suggest focusing on the “trimmed mean,” a statistical construct that disregards all goods and services whose prices change by the largest amounts (either up or down). In recent months, the trimmed mean CPI shows suggest that inflation has edged lower, but remains between 1½ and 2 percent per year….