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lt. will, be noted that the process can be described up to 
this point without any reference to. income- We may regard the 
states of the system represented by the elements of*, the matrix 
as "grades”■ or "age'* -'possibly carreer, age or age in earning 
life,, although in conformity with Champernowne we referred to 
them as income classes. " 
We have now to define the income in relation to the class 
intervals of the matrix: The lower limit of class 1 is 
taken to he the minimum'income. ¥e may choose the income 
units such that the minimum income is unity, i.e. on the 
logarithmic scale it is zero. The income y^ at the lower 
limit of successive income classes K is defined hy 
Xh 
7*r = e 
or In y K = Kh 
where h is the size of the class interval on the log scale 
1) 
The difficulties arising from the discrete representation of 
a continuous income variable in the matrix do not concern 
us here. See £ioJ p. 62. 
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