322 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
‘hat the relative productivity of two primary inputs depends 
only on their distance from each other in time, and this is 
exactly what hypothesis (d) says. 
3. JUSTIFICATION OF THE MODEL WITH RESPECT TO ITS CON- 
SEQUENCES 
The main points on which conclusions derived from the ex- 
ponential model are justified are the following: 
a) Small Inter-country Differences in the Value of the Capital- 
Output Ratio at the Same Point of Time 
323. The relation 
(323-1) 
yo 9 
+0 2 
shows that if ©, as a technical constant applies to the different 
countries considered, the capital-output ratio y should change 
but little, for according to the formula such changes cannot be 
very great at observed rates of interest and with a value of ©, 
of about 4. 
Thus, for 1913, I have calculated ®, as (?): 
United States 
France . . 
Great Britain 
Average . 
3-44 
3.83 
3.67 
2.64 
* Relation 251-6. 
?) ATLAIS (1060 A), D. 715; (1962 A), PP. 52-53. 
11] Allais - pag. 126