Family income and child health in the UK : The age-profile in the gradient

A large amount of literature shows a positive correlation between socio-economic status and health in adulthood (Adler et al., 1994; Deaton and Paxson, 1998; Deaton and Paxson, 1999; Van Doorslaer et al., 1997; Wilkinson and Marmot, 2003). Recent research initiated by Case et al. (2002) investigates whether the income gradient observed in adulthood has antecedents in childhood. Findings firmly establish that family income is positively related to child general health in Australia (Khanam et al., 2009), Canada (Currie and Stabile, 2003), Germany (Reinhold and Jurges, 2011) and the US (Case et al., 2002; Condliffe and Link, 2008). Moreover, the correlation between family income and child health strengthens as children grow older in Canada and the US (Case et al., 2002; Condliffe and Link, 2008; Currie and Stabile, 2003). In contrast, findings on the relationship between family income and child health in the UK are not clear cut. First, descriptive evidence by Patrick West suggests that there is a socio-economic gradient and that this gradient decreases between childhood and youth (West, 1997; West and Sweeting, 2004), using British and Scottish data. Second, Currie et al. (2007) highlight that there is a gradient but that it does not increase with age, using six waves of the Health Survey for England. Third, in contrast, Case et al. (2008) provide evidence that the gradient does increase with age, using three additional years of data from the Health Survey for England. Fourth, Burgess et al. (2004) and Propper et al. (2007) investigate whether the gradient represents a causal effect of income on health as opposed to heterogeneity and conclude that there might not be any causal effect of income on child health, for a cohort of young British children. Although this literature gives complementary insight into the income gradient in child health in the UK, it is subject to limitation. First, the samples that are used are relatively small, which can explain why the results are sometimes contradictory. We think that a larger dataset might help get more stable results. Second, the previous literature does not examine the turning points in the evolution of the gradient with age. Burgess et al. (2004) and Propper et al. (2007) focus on children less than 7. Case et al. (2008) and Currie et al. (2007) study children ages 0-15, using four age groups only (children ages 0-3, 4-8, 9-12 and 13-15), so they cannot observe any evolution of the gradient that would takes place within group ages. In order to find out the turning points for the evolution of the gradient in childhood, it is necessary to examine the gradient for children ages 0-17 and for more precise age groups. This in turn requires a large dataset. Third, a final limitation of the earlier literature on the UK is that it uses cross-sectional data which makes it difficult to study the mechanisms underlying the evolution of the gradient with age. Understanding these mechanisms is all the more important as different mechanisms call for different answers from a policy perspective. Currie et al. (2003) argue that the evolution of the gradient with age can be due either to a prevalence or to a severity effect of chronic conditions. On the one hand, there is a prevalence effect if children from poorer families may be more likely to be subject to health shocks, in the form of new chronic conditions, than their wealthier counterparts. To counteract the prevalence effect, it is necessary to address the reasons