Household income is a funny collective measure. If housing becomes less affordable, household income increases, as kids stay longer with their parents. And if housing becomes more affordable, household income decreases, as kids move out earlier.
I think a better measure would be household income divided by number of adults in the household. Possibly with some consideration for the number of children in the household.
E.g. OECD normalizes household income by household size:
> Household income is adjusted for differences in the needs of households of different sizes with an equivalence scale that divides household income by the square root of household size. The adjusted income is then attributed to every person in the household.
