= 
4 
PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
[f the intervals between 0 and 1 and between 1 and 2 are the 
same, then ® =1. 
The effect of this method of projection will be to change 
each coefficient in the way that it has been changing in the 
past. This can be only approximately correct, and so it is of 
particular importance to get as much direct information from 
outside as possible. For example, in Britain between 1954 and 
1960 the oil component of the input of fuel into electricity ge- 
neration rose from a very small figure to nearly 20%. A con- 
linuation of this trend would make oil the dominant fuel input 
by 1970. But we know that this particular trend will not 
continue as in the past because of the kind of fuel used in 
generators that have been built very recently and are planned 
for the immediate future. The direct information can come 
either from current statistics of input-output coefficients which 
are available in a limited number of cases, for example coal 
used in coke ovens, or from outside knowledge, as in the case 
of oil used in the generation of electricity. 
We have used such direct information wherever possible 
and then applied (IV. 58) to the remaining elements of the 
input-output matrix. We have then discussed the results of 
this exercise cell by cell and changed the projections subjectiv- 
ely if this seemed desirable. The results of such a survey are 
illuminating. For example, we were surprised to find that in 
our projections the coefficient for machine parts and repairs 
into agriculture rose, indicating a greater use of machinery, 
while the coefficient for petroleum products fell. We were told 
that this was not really surprising because of the substitution 
of the less processed and cheaper diesel oil for petrol and that 
our results were a reflection of this particular type of fuel 
economy. We therefore did not change our provisional result 
in this case, although we did in manv others. 
d) Output levels. If we bring together the foregoing cal- 
culations, we can estimate output levels in 1970. In the preli- 
11 Stone - pag. 70