378 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 All the statistical data analysed lead to the conclusion that in present conditions ®_ is of the order of marnitude @ = the time unit used being the year, and we have probably (4 38< O< 1.6. The increase in real consumable income Rg which can be had by moving from a value © to the value ®, corresponding to the maximum value of Re is equal to (410-3) KR = wo ee 8 g R° or, from relation (410-1) (410-4) 2 0 © eo -—e ® In each situation, the value of the difference 7 - ¢ is given by the relation (251-5) 410-3, 1-6 rz 5 € (1) This question cannot be taken up -here. 11 Allais - pag. 187