Price measurement

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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Policy and Measurement

Policy, especially monetary policy, is about numbers. Is inflation close to target? How fast is the economy growing? What fraction of the workforce is employed?  And, what is the relationship between the policymakers’ tools and their objectives? Answering all of these questions requires measuring a broad array of economic indicators, with consumer prices high on the list. In this post, we discuss some of the pitfalls in measuring prices.

Price indices of the sort that we use today have been around since the late 19th century. In the United States, near the end of World War I, the National Industrial Conference Board starting constructing and publishing a cost-of-living index. This work was eventually taken over by the Bureau of Labor Statistics (BLS). Over the past century, the theory of price indexes (see, for example, here and here) and the means of measurement have both moved forward substantially.

With the advent of inflation targeting, price indices have taken on a new prominence. If monetary policymakers are going to focus on controlling inflation—setting numerical targets for which they are then held accountable—then the construction of the price index itself becomes an issue. What is included and how can become critical to the way policy is conducted and to the achievement of the stated objective, namely price stability....

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