Analyses based on the data-sets of British birth cohort studies have produced differing findings on trends in intergenerational income and intergenerational class mobility. As between a cohort born in 1958 and one born in 1970, income mobility appears to show a sharp decline, while class mobility remains essentially constant. We investigate how this divergence might be explained. We find no evidence that it results from the differing subsets of data that have been used. However, we show that for both birth cohorts a stronger association exists between father’s class and child’s class than between family income and child’s earnings (and likewise between father’s class and child’s educational qualifications than between family income and child’s qualifications) - and that these differences are especially marked in the case of the 1958 cohort. We therefore argue that it is the surprisingly weak influence exerted by the family income variable for this cohort in these - and other - respects that must be seen as crucial in accounting for the inter-cohort decrease in income mobility that shows up. We point to evidence that as between 1974 and 1986, the years when the family incomes of children in the two cohorts were determined, the transitory component of earnings fell, so that the one-shot measure of such income made at the earlier date will be a less good measure of permanent income than that made at the later date. We therefore suggest that, at least to some extent, the apparent decrease in income mobility may come about in this way. But even if the finding is taken at face value, it would still appear the case that the class mobility regime, as well as having greater temporal stability than the income mobility regime, tends also to be stricter in the sense of entailing a stronger intergenerational association between origins and destinations and one that thus more fully captures continuities in economic advantage and disadvantage.
2009. , 43 p.