Since this is household income, and not individual income, perhaps we are seeing the hourglass effect because in some homes, one person works, and in other homes, two people work.
Secondly, perhaps it is the market which is driving the income, rather than the other way around. If a household stretched to buy a home, you have two people in the house working, if a household rents, they have one income.
Those stuck in the middle – those who are tired of renting but do not make enough buy a home – have left.
