How will you be running a 400 million people country?

I'd write some document, call it the law-of-the-land, make everyone that wanted to stay agree with it, everyone else could leave. It would set up some very precise and strict rules about what I (the government) was allowed to do. I would let individuals cooperate as they see best. I would protect people's rights and punish those who infringe their neighbors. I'd probably follow these rules for a couple hundred years, then say "screw it" and do whatever I wanted.