Thursday, July 12, 2007

Explaining the CPI-U

This Monday's Outside the Box E-Letter by John Mauldin features a great publication from the Congressional Budget Office. To whet your appetitie, here's the introduction:

This week in Outside the Box we look at a Congressional Budget Office publication that dives us the details on how the consumer price index for all urban consumers (CPI-U) is created. This is, as the CBO posits, the best-known official measure of inflation.

The brief that follows will venture to explain the methods used to construct the CPI-U, and how and why the index's estimates of inflation might differ from a consumer's perceptions of price changes. Though I think this article may be somewhat akin to discovering what components comprise the makeup of sausages (knowledge that is usually best left undiscovered), it is useful to understand just how the inflation data is constructed. Some of the points they make are controversial, especially when it comes to "hedonic" pricing, which they refer to as "shifts in the quality of goods and services over time." This does allow for some quite subjective influence in the inflation numbers. While I will visit this topic in a later letter, it is good to know what is and is not being measured.

Wednesday, July 11, 2007

Bernanke Speech : 07-10-2007

This Tuesday, Ben Bernanke spoke to the NBER-sponsored Summer Institute regarding inflation expectations and inflation forecasting. On inflation expectations, Bernanke summarized recent literature focusing on defining and measuring inflation expectations, and how to use that information to forecast and control inflation.

The more interesting part of the speech concerned how the Federal Reserve Board forecasts inflation. Rather than recapitulating the most intriguing portion, I've included it below:

The Board staff employs a variety of formal models, both structural and purely statistical, in its forecasting efforts. However, the forecasts of inflation (and of other key macroeconomic variables) that are provided to the Federal Open Market Committee are developed through an eclectic process that combines model-based projections, anecdotal and other "extra-model" information, and professional judgment. In short, for all the advances that have been made in modeling and statistical analysis, practical forecasting continues to involve art as well as science.

The forecasting procedures used depend importantly on the forecast horizon. For near-term inflation forecasting--say, for the current quarter and the next--the staff relies most heavily on a disaggregated, bottom-up approach that focuses on estimating and forecasting price behavior for the various categories of goods and services that make up the aggregate price index in question. ... In making very near-term price forecasts, the staff also uses diverse information from a variety of sources, such as surveys of prices of gasoline and other important items, news reports about price-change announcements, and anecdotal information from our business contacts. Conceptually, one might think of this effort to distinguish transitory from persistent price changes as a more nuanced way of estimating the underlying inflation trend, analogous to the trend measures provided by more mechanical indicators such as trimmed-mean or weighted-median inflation rates.

An accurate forecast of very near-term inflation is important not only for its own sake but also because it provides a better "jumping-off point" for the longer-term forecast. Because inflation continues to exhibit some inertia, improved near-term forecasts translate into more-accurate longer-term projections as well.

For forecasting horizons beyond a quarter or two, detailed analyses of individual price components become less useful, and thus the staff's emphasis shifts to inflation's fundamental determinants. Food and energy inflation are forecasted separately from the core, using information from futures prices and other sources. However, forecasts of core inflation must take into account the extent to which food and energy costs are passed through to other prices.

In addition to the above, Bernanke notes that the Board uses a range of econometric models to forecast inflation at longer horizons. However, the models' estimates are not so robust as to permit sharp inferences, so the Board's long-term forecasts "inevitably reflect a substantial degree of expert judgment and the use of information not captured by the models." Finally, he turns to the Board's use of inflation expectations in forecasting inflation.