America's affordable housing crisis has reached a new milestone

The affordable-housing crunch worsened last year.
In the final quarter of last year, Americans spent the highest share of their incomes on mortgage payments since 2010, according to real estate company Zillow. 
The economy's improvement after the housing crash generated new buyer demand for housing, even though the homeownership rate remained historically low.
Simultaneously, incomes rose slowly, and affordable housing inventory — especially in populous cities &mda