Economics Thought Experiment for the Day

This is slated for a busy day, so my substantial post creation abilities are limited. However, I wanted to throw out for discussion a thought experiment that has been bumping around my head for a few weeks. (And yes, this is probably something of a political/economic Rorschach test.)

Picture, if you will, that in an effort to guarantee a minimum standard of living for all Americans, a law was passed guaranteeing a minimum income to every US citizen aged 18 or over. According to this law, if you are 18 or over, you will always make at least $24,000/yr. Hourly wages and work week are in no way fixed -- in fact, the minimum wage is abolished, but all your wages up to 2k/mo are collected as a payroll tax and sent to the Central Payroll Administration. Every citizen 18 or over, regardless of whether he or she works, receives a check for $1000 on the 1st and 15th of every month (generally conveniently deposited to the bank account of your choice.) If you work at a job that pays more than 24k, you receive the rest of your salary directly from your employer.

This means that single people are guaranteed an income of just over twice the poverty line, and couples have a combined income about twice the poverty line for a family of four.

My theory is, under such a system: unemployment would go up (a lot); mobility between economic classes would decrease; income inequality would increase and the productivity of those who did work would also increase. Why I can go into later if it seems non-obvious.

Thoughts?