Wednesday, April 13, 2011

CNBC Jumps the Shark: Or, Why the Conspiracy Theories About CPI Are Dead WRONG

From CNBC:
Inflation, using the reporting methodologies in place before 1980, hit an annual rate of 9.6 percent in February, according to the Shadow Government Statistics newsletter.
Never mind that Shadowstats has been debunked.

Let's assume that inflation is actually at 9.6%. That means the entire Treasury market is underwater by a little under 6% or 600 basis points. While the markets may not be perfectly efficient, they are not that inefficient either -- not by a long-shot. I haven't watched CNBC for a long time -- as in years. Now I now why. They are a financial news channel that doesn't know anything about finance.

Silver Oz has the following links to share

The effect of adjustments

Owners Equivalent Rent

Some Common Misconceptions about CPI:

When the cost of food rises, does the CPI assume that consumers switch to less desired foods, such as substituting hamburger for steak?

No. In January 1999, the BLS began using a geometric mean formula in the CPI that reflects the fact that consumers shift their purchases toward products that have fallen in relative price. Some critics charge that by reflecting consumer substitution the BLS is subtracting from the CPI a certain amount of inflation that consumers can "live with" by reducing their standard of living. This is incorrect: the CPI's objective is to calculate the change in the amount consumers need to spend to maintain a constant level of satisfaction.

Specifically, in constructing the "headline" CPI-U and CPI-W, the BLS is not assuming that consumers substitute hamburgers for steak. Substitution is only assumed to occur within basic CPI index categories, such as among types of ground beef in Chicago. Hamburger and steak are in different CPI item categories, so no substitution between them is built into the CPI-U or CPI-W.

Furthermore, the CPI doesn't implicitly assume that consumers always substitute toward the less desirable good. Within the beef steaks item category, for example, the assumption is that consumers on average would move up from flank steak to filet mignon if the price of flank steak rose by a greater amount (or fell by less) than filet mignon prices. If both types of beef steak rose in price by the same amount, the geometric mean would assume no substitution.

In using the geometric mean the BLS is following a recognized best practice for statistical agencies. The formula is widely used by statistical agencies around the world and is recommended by, for example, the International Monetary Fund and the Statistical Office of the European Communities.

Is the use of "hedonic quality adjustment" in the CPI simply a way of lowering the inflation rate?

No. The International Labour Office refers to the hedonic approach as "powerful, objective and scientific". Hedonic modeling is just one of many methods that the BLS uses to determine what portion of a price difference is viewed by consumers as reflecting quality differences. It refers to a statistical procedure in which the market valuation of a feature is estimated by comparing the prices of items with and without that feature. Then, for example, if a television in the CPI is replaced by one with a larger screen and higher price, the BLS can make an adjustment to the price difference by estimating what the old television would have cost had it had the larger screen size.

Many of the challenges in producing a CPI arise because the number and types of goods and services found in the market are constantly changing. If the CPI tried to maintain a fixed sample of products, that sample quickly would shrink and become unrepresentative of what consumers were purchasing. Each time that an item in the CPI sample permanently disappears from the shelves, the BLS has to choose another, and then has to make some determination about the relative qualities of the old and replacement item. If it did not--for example, if it treated all new items as identical to those they replaced -- significant upward or downward CPI biases would result.

Critics often incorrectly assume that BLS only adjusts for quality increases, not for decreases, and that hedonic adjustments have a large downward impact on the CPI. On the contrary, BLS has used hedonic models in the CPI shelter and apparel components for roughly two decades, and on average hedonic adjustments usually increase the rate of change of those indexes. Since 1998, hedonic models have been introduced in several other components, mostly consumer durables such as personal computers and televisions, but these newer areas have a combined weight of only about one percent in the CPI. A recent article by BLS economists estimated that the hedonic models currently used in the CPI outside of the shelter and apparel areas have increased the annual rate of change of the All Items CPI, but by only about 0.005 percent per year.

Has the BLS selected the methodological changes to the CPI over the last 30 years with the intent of lowering the reported rate of inflation?

No. The improvements chosen by the BLS that some critics construe to be a response to short term political pressure were, in fact, the result of analysis and recommendations made over a period of decades, and those changes are consistent with international standards for statistics. The methods continue to be reviewed by outside commissions and advisory panels, and they are widely used by statistical agencies of other nations.

Moreover, the sizes and effects of the changes implemented by the BLS are often over-estimated by critics. Some have argued that if the CPI were computed using the methods in place in the late 1970s, the index would now be growing at a rates as high as 11 or 12 percent per year. Those estimates are based on the belief that the use of a geometric mean index lowered the annual rate of change of the CPI by three percentage points per year, and a belief that other BLS changes, such as the use of hedonic models and rental equivalence, have lowered the growth rate of the CPI by four percentage points per year.

Neither belief is supported by evidence. BLS calculations have shown that the geometric mean formula has reduced the annual growth rate of the CPI by less than 0.3 percentage points. Hedonic quality adjustments for shelter regularly increase the rate of change of the CPI, and those for apparel have had both upward and downward impacts at different points in time and for different types of clothing. The BLS estimates that the overall impact of hedonic quality adjustments in use in other categories has been extremely small. Furthermore, if the CPI were using the pre-1983 asset-based method instead of rental equivalence to measure homeowner shelter cost it would yield a sharply lower current measure of shelter inflation, given that house prices are now declining in many parts of the country