Decomposing Housing Unaffordability

A US household is considered ‘rent burdened’ when its rent exceeds 30% of its income. This simple ratio can be decomposed to better understand the sources of unaffordability across space. To demonstrate this new approach, I rewrite the equation for rent burden as a sum of four factors: rent gap, income gap, excess size cost, and demographic baseline, and show that US rental unaffordability is mostly the result of low incomes. Focusing on the New England region, however, I show that high rent is the primary cause of unaffordability in high-cost, high-wage metro areas. This decomposition can help affordability advocates prioritise strategies appropriately across space.