Altogether, humankind had spread over less than one-eighth of the galaxy. Expansion was somewhat self-limiting. The U.S. had not been able to hold a colony at two hundred light-years distance. At fifteen hundred light-years, most nations could consider their colonies temporary holdings. Any people it took you two months to reach were not going to pay your taxes or obey your laws. That was human nature. - Wolf Star, Tour of the Merrimack #2