More Research on the Canadian Health Care Income Gradient

American pundits and activists behave like it doesn't even exist, but income is not only important it is possibly more important in Canada than it is in the U.S. Anyway, in Empirical Economics I found this paper to be interesting by Sun and Stengos:

The absolute health income hypothesis revisited: a semiparametric quantile regression approach

This paper uses the 1998–1999 Canadian National Population Health Survey data to examine the health–income relationship that underlies the absolute income hypothesis. To allow for nonlinearity and data heterogeneity, we use a partially linear semiparametric quantile regression model. The “absolute income hypothesis” is partially true; the negative aging effects appear more pronounced for the ill-healthy population than for the healthy population and when annual income is below 40,000 Canadian dollars.

I wonder if there is a comparable study in the US? The absolute income hypothesis (AIH) suggests that increasing a persons income will improve their health, but at a diminishing rate (aka "concavity"). The alternative theory is the relative income hypothesis, which says it is your income relative to your peer group that determines your health outcomes. Support for the AIH theory suggests that we want to address health care outcomes by focusing on income growth.

This paper shows that the AIH holds but is not "globally concave," in that it does not hold for the entire spectrum of the population, but instead applies differently across age groups. The paper is very good so, if you are familiar with quantile regressions, I recommend those with an interest to have a read.