704 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
The characteristic function o(t, 0) is therefore invariant. 
Also, we have from (223-7) and (231-5) 
(231-6) 
#(e) - bli-p) °° 
b(i) elo) 
Since 
b (2-p) > d (1) 
for p> o0 
the function @ /¢ declines from a value of above 1 to 0 when 0 
increases indefinitely. 
Average Production Period 
232. We have from (112-2) and (231-5) 
O05 (0) a0 
(232-1) 
_[Tog(e) ¢° 4 
/ 0) 0 
3 
Now, from (220-1), we have 
(232-2) dé(i) __ 1 [Top(e)e "do 
i k y. 
[11] Allais - pag. 08