COST OF LIVING INDEXES COMPARED 109 
To test out this theory Table 6 has been constructed. 
This gives the Bureau's index number series for each item 
separately and for all combined, on the basis of the 1918 
weights—that is, the official number. It also gives, in the 
last column, a new series for the total cost of living, based 
on the same index numbers for the major items, but com- 
bined on the basis of 1913 weights. In other wotds, from 
the known distribution of expenditures in 1918 and known 
increases in prices between 1913 and 1918, the distribution of 
expenditures in 1913, the base period, has been computed! 
and substituted in the series for the official weights based on 
the 1918 distribution. The difference between the two series 
1s seen to have increased as the prices of the different items 
advanced in varying proportions. At the peak, when the cost 
of clothing had increased 187.5%, and that of housing only 
34.9%, the maximum difference, 9 points, occurred. Where, 
however, increases in the cost of the major items were more 
nearly uniform and none of them so tremendous, the two 
series were identical, or nearly so. In other words, at the 
peak of prices, with very uneven price increases recorded for 
the different items, the advance in the total cost of living 
obtained by using wartime weights was greater than would 
have been the case had weights been used based on pre-war 
consumption. During most of the period of the series, the 
difference due to the effect of the weights was negligible. 
This test assumes, however, the consumption of the same 
goods and services in 1913 as in 1918. In other words, it 
changes the series only to eliminate the effect of price in- 
Creases on expenditures. To convert the Bureau of Labor 
Statistics series to a pre-war basis as regards consumption 
habits, pre-war weights based on these habits should be 
used. For this purpose, the increases in cost of the separate 
Items since 1913, as found by the Bureau of Labor Statistics, 
have been multiplied by the weights used in the National 
Industrial Conference Board series for each date on which the 
Bureau has figures. These weights are based on pre-war 
consumption. The results are shown on the next page. 
! The 1913 weights were determined by using the geometric reversal; the 
arithmetic produces a total in excess of 100. 
*See p. 32 of this volume.