A federation often emerges from an initial agreement between several separate states. The purpose can be the will to solve mutual problems and to provide for mutual defense or to create a nation-state for an ethnicity spread over several states. The former was the case with the United States and Switzerland. However, as the histories of countries and nations vary, the federalist system of a state can be quite different from these models. Australia, for instance, is unique in that it came into existence as a nation by the democratic vote of the citizens of each state, who voted "yes" in referendums to adopt the Australian Constitution. Brazil, on the other hand, has experienced both the federal and the unitary state during its history. Some present-day states of the Brazilian federation retain borders set during the Portuguese colonization (before the very existence of the Brazilian state), whereas the latest state, Tocantins, was created by the 1988 Constitution for chiefly administrative reasons.