For instance, if market incomes became more unequal and social preferences towards inequality remained unchanged, a given extent of redistribution would appear less costly in terms of overall social welfare and additional redistribution would be desirable. Conversely, reducing inequalities would be seen as less pressing if preferences became less egalitarian (say because of more widespread concern over adverse incentive effects of redistribution), while market-income inequalities remained unchanged. Over longer periods of time, one would expect to observe changes in both social preferences and the distribution of market incomes. The dispersion of market incomes has in fact changed considerably.