The Bureau of Labor Statistics is thinking about reporting inflation data out to three decimal places:
The government is considering providing more information each month on its most closely watched inflation gauge as a way to dampen financial market volatility.
The Bureau of Labor Statistics is exploring a change to its Consumer Price Index that would provide details on inflation out to three decimal places instead of just one decimal place currently, BLS official Patrick Jackman said Monday.
If BLS officials decide to make the change, it could take effect as soon as next year with release of the January CPI report, Jackman said.
….. Financial markets have been roiled in recent months by the CPI report, especially the figure on core inflation, which excludes food and energy.
The core CPI has risen by 0.3 percent in each of the past four months, a jump from the 0.1 percent and 0.2 percent readings for the previous 12 months.
That uptick in inflation pressures has raised worries on Wall Street that inflation could be getting out of control, especially after Federal Reserve Chairman Ben Bernanke noted the acceleration in the CPI price measure in a speech in June.
However, private economists argued that some of the 0.3 percent readings were overstating inflation and would have looked less worrisome if the government presented the inflation numbers out to three decimal places.
For example, an increase in core prices of 0.249 percent would round to an increase of 0.2 percent while an increase of 0.251 percent would be rounded up to 0.3 percent.
While the minor month-to-month rounding issues don’t have much impact on how inflation is reported for a longer period of time such as 12 months, the numbers do have impacts, especially in financial markets, over a shorter period of time.
Based on the markets’ hypersensitivity to single tenths of a percent, I can understand the idea that the BLS might want to move to two decimal reporting if, as it appears, they have the data to support it. They can do whatever they need to in the background, even using three-decimal calculations, while only reporting two.
But reporting to three decimal places assumes a level of precision in measuring prices in a $13 trillion economy, with billions (if not trillions) of transactions every day, that I would think can’t possibly exist. I can see how BLS might be able to tell us with a straight face that inflation was .11% in a given month and not .12%. But I don’t think there’s any way they can tell us with any kind of confidence that inflation was .115% vs. .116%. Nobody’s that good, and the BLS shouldn’t pretend to be. Looking at how they subsequently have to revise their figures is evidence enough that going out to three decimal places in reporting would be a mistake.
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UPDATE, August 19: Commenter 3 tells me that BLS doesn’t revise CPI. Comment 4 explains why I thought they did. The last sentence of the original post above has been crossed out for that reason.
UPDATE 2, August 20: Here’s what BLS decided to do:
Beginning next year, the government’s main inflation gauge will be more precise, a change officials hope will limit financial market volatility.
The Bureau of Labor Statistics said Wednesday it will publish the Consumer Price Index and its component indexes out to three decimal places, rather than just one decimal place, starting with the January CPI report that will be released in February 2007.
Officials said the change is being made so that financial markets and agencies such as the Federal Reserve will have more information on price changes.
BLS official Patrick Jackman said by making public the more precise index figures, those interested will be able to do their own calculations of the month-to-month percent changes.
Financial markets have been jolted in recent months by the CPI report, especially the figure on core inflation, which excludes food and energy.
The core inflation increase reported Wednesday for July was a more moderate 0.2 percent. But that came after four straight months when core inflation was rising by a more worrisome 0.3 percent each month.
Private economists argued that some of the 0.3 percent readings were overstating inflation and would have looked less threatening if the government had presented the index figures on which those readings were based out to three decimal places.
An increase of core prices of 0.249 percent would round to an increase of 0.2 percent while an increase of 0.251 percent would be rounded up to 0.3 percent even though there was little difference in the two figures.