Measures of segregation Segregation measures have generally been expressed as summations over all the occupations under consideration. Here male occupations are defined as those where the proportion of men is greater than the proportion in the labour force as a whole, with a corresponding definition for female occupations. As well as being more compact, the 2 X 2 table has the important advantage of making clear just what is being measured. The limitations of non-symmetrical measures are then obvious. The Index of Dissimilarity can be seen to be a difference of the column proportions in the table.
SR is a weighted version of the difference of row proportions.
These weightings vary with the gender composition of the labour force but none is in any way relevant to the degree of segregation. Similar standardisation of IP and WE gives ID, the difference of column proportions. Essentially the problem is that there are no statistics of association which are independent of the marginal totals of a table. It is true that each difference of proportions has what is known as 'marginal independence' with respect to one pair of marginal totals, but this only applies to the socially unlikely process of the relevant row or column being multiplied throughout by a constant. In the real world, social processes are quite different and in particular people move among occupations according to demand for labour.