4 
To find the tail of the steady state distribution P(y^) we 
sum (2) from X to oo and obtain p K . Thus 
In P(y^) = In p . ^ In y K 
„'I 
and, putting -h In p = oC we have 
In P(y^) - -oc In 7k 0) 
Evidently the crucial feature of the model is the geometric 
distribution of the recurrence time. This relates here to 
the life-time of the persons as income receivers; since 
promotion is automatic, the age of the system is measured 
in income classes K, The age, or spent life-time, is 
geometrically (approximately exponentially) distributed. 
Since the income is also an exponential function of i£ , 
the Pareto law results from an elimination of time K from 
1) 
the two exponential functions. ' 
This is exactly the same pattern of explanation as was used 
l% - 2.^11/23 
in other fields by Simon cW and myself and 
[yv tM-- 
which is^directly descended from Yule CJj who used it 
2. 
to explain the frequency of species in genera. According to 
^Altfbqugh Champernowne' sNo^odel is more complicasted than the 
above^x^he essential feattip^s remain the same (oitiy p in 
the solution is replaced by b, the solution of a difference 
equation).