Consumer price index is a common measure of the
overall price change in modern economies, which represents a broader indicator
of the cost of living. For Japan, this measure has become extremely important during
the last decade because of its very low if not negative value. Economists usually
panic when cost of living decreases. Price deflation is a major danger for long
term economic growth since bank credits (read investments) are highly
suppressed. Everybody knows: no investment
- no growth. Hence, any news about positive inflation is
welcome and no tricks are bed to get this news.
Figure 1 shows the evolution of two integral inflation
measures for Japan: the cumulative CPI inflation and the cumulative GDP
deflator (DGDP). The latter covers all
prices in a given economy, while the CPI only a part of them related to
consumer goods and services. By definition, the DGDP should nest all CPI items,
but the CPI is calculated in a different way based on a basket of goods and
products with their shares fixed over a few years. In that sense, the CPI does
not follow all economic changes up.
The graphs in Figure 1 are different from
inflation indices expressing the absolute change in price level. The cumulative
inflation time series describes the relative change in the overall price. The difference between the DGDP and CPI is
dramatic and increases since 1974. From 1974 to 2012, the difference between
the cumulative inflation reached 0.37, and the rise in CPI inflation is by ~50%
larger than that in the DGDP.
What is the reason?
The DGDP plays a different role in economics.
This is the most important value for real GDP growth. Real GDP is not a
measured macroeconomic variable, but rather the ratio of the nominal GDP and
the GDP price deflator. Larger DGDP values give smaller real GDP.
So, this is very important to keep the DGDP as
low as possible and the CPI as high as possible. This is a nasty
trick which, mathematically, must result in negative absolute prices of all
goods and services not in the CPI. Do
not trust the CPI estimates in Japan. Figure 2 shows two countries without such
a dramatic difference between CPI and DGDP: Austria and France. In the USA, the
difference between CPI and DGDP has been also increasing since 1978 (Figure3).
But the FRB prefers to use Purchase Consumer Expenditures (PCE) instead of the
CPI to characterize consumer prices. Figure 4 shows that the DGDP and PCE are
similar in the USA.
Figure 1. The evolution of cumulative rate of CPI
inflation and GDP deflator in Japan.
Figure 2. The evolution of cumulative rate of CPI inflation and GDP deflator in Austria and France.
Figure 3.
The evolution of cumulative rate of CPI inflation and GDP deflator in the
USA.
Figure 4.
The evolution of cumulative rate of PCE inflation and GDP deflator in the
USA.
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