A central feature of the US economy is the economic freedom afforded to the private sector by allowing it to make the majority of economic decisions concerning the direction and scale of what to produce. Steady growth of the labor force and demographic shift have helped determine the health of the US economy,with the former being both cause and effect of almost constant economic expansion,and the latter being important to the capacity of the US economy to adapt to changing conditions. Another important feature of the US economy is the application of science and technology in production.Encouraging science and innovation,the US has been a leader in scientific research and technological innovation since the late nineteenth century. All these features have contributed to the growth of the US into a developed country.