Although the legislative powers of the states are defined in the Constitution, the real power of the Australian Premiers has been declining steadily ever since Federation in 1901, as the power and responsibility of the national government has expanded at the expense of the states. The most important transfer of power came in 1943, when in the interests of national unity during World War II the states gave up their power to levy their own income taxes to the Commonwealth. Since then the states' finances have essentially been controlled by the Commonwealth.