Price measurement bias

The Price is Not Right: Measuring Inflation in a Pandemic

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….

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Inflation and Price Measurement: A Primer

People use a variety of statistics to gauge how the economy is doing. It is fairly straightforward to measure nominal GDP, so the challenge of estimating real economic growth arises from the need for accurate measures of prices. Price measurement also is key for inflation-targeting central bankers, who need a number as a guide and for public accountability. To be credible, that number must be based on an index constructed using established scientific methods.

Reflecting a set of well-known (and nearly insurmountable) difficulties, measured inflation has an upward bias. That is, the inflation numbers that statistical agencies report are consistently higher than the theoretical construct we would like to compute. As a consequence of this upward bias in inflation measurement, our estimates of growth in real output and real incomes are systematically too low.

The big question today is whether the bias in inflation measurement, and hence the bias in the measurement of growth, has increased in recent years. As Martin Feldstein describes in detail, the answer to this question is important, as it affects how we collectively view long-run progress. If published statistics show sluggish real growth, as well as slow growth in real wages and incomes, then people may be unduly pessimistic. A worsening bias would add to that pessimism.

In practice, however, careful recent analysis suggests that inflation measurement bias has not changed much since the early 2000s….

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The case for a higher inflation target gets stronger

For several years, economists and policymakers have been debating the wisdom of raising the inflation target. Today, roughly two-thirds of global GDP is produced in countries that are either de jure or de facto inflation targeters (see our earlier post). In most advanced economies, the target is (close to) 2 percent. Is 2 percent enough?

Advocates of raising the target believe that central banks need greater headroom to use conventional interest rate policy in battling business cycle downturns. More specifically, the case for a higher target is based on a desire to reduce the frequency and duration of zero-policy-rate episodes, avoiding the now well-known problems with unconventional policies (including balance sheet expansions that may prove difficult to reverse) and the limited scope for reducing policy rates below zero.

We have been reticent to endorse a higher inflation target. In our view, the most important counterargument is the enormous investment that central banks have made in making the 2-percent inflation target credible. Yet, several lines of empirical research recently have combined to boost the case for raising the target….

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