58 COST OF LIVING IN THE UNITED STATES 
cach index number by its respective weight, adding together 
the products and dividing by the sum of the weights. This 
method is shown in the following tabulation: 
Vietop oF CoMPUTING NATIONAL INDUSTRIAL CONFER- 
ence Boarp INDEx NumBers oF THE ToraL Cost oF 
Living 
July, 1914 = 100 
(tem 
LW 
Weight in Budget | 
Na 
Index Numbers, 
December. 1925 
Col. 2% Col. 1 
Food. ...... -. 
Shelter. ......... Cee an 
AON. oo oon vious mmmene 
Fuel and light. ... 
Sundries. .........o.-- 
Weighted average of all items... .) oo 
a This fioure includes estimates of changes in the cost of anthracite substitutes. 
71.546 
7 31.329 
07 | 23.364 
1662 9.2062 
176 35.904 
171.439 
Tue MontHLY INDEX NUMBER 
The process of making up the cost of living index numbers 
»f the National Industrial Conference Board, just described 
in detail, relates to the comprehensive data collected three 
times a year in March, July and November of each year, 
and in December, 1925. In addition to these numbers, from 
January, 1920 to October, 1925, the Board also assembled 
‘information for intermediate months on a somewhat more 
limited basis as regards sources of information. The basic 
budget and the method of collecting and combining current 
price data are identical with those for the more comprehen- 
sive surveys. 
These monthly reports were started at a time when prices 
were changing very rapidly, and have always been considered 
in the nature of Interim estimates indicative of tendencies 
rather than as definite measurements. As a matter of 
fact, however, experience with these monthly estimates 
indicates that for the budget as a whole the figures give a 
very fair measure of the trend in the cost of living in those 
months when complete reports are not available. For the 
separate items, the numbers have not had the same validity. 
As already noted, beginning in December, 1925, it is planned