[logfromblammo]

You hit the bullseye with this one. Parents remain unmarried in a monogamous, cohabiting relationship because the government pays them to not get married. Every benefit that has a household means test attached is an additional incentive to strategically realign the membership of your households.

So you designate one household as the mooch household, and one as the worker household. The latter tends to be ineligible for all manner of otherwise useful benefits, working full-time at minimum wage, and benefits may even be curtailed working part-time. The other can collect the maximum available benefits.

This also leads to some strange behavior in states that have common-law marriages.