Producers independently make investment decisions based on factors like replacing machinery, expanding production, and building new facilities. The level of national income does not decisively determine investment in the way it determines consumption. Four key factors influence autonomous investment: 1) the technology level, 2) the interest rate, 3) expectations of future economic growth, and 4) the rate of capacity utilization. Investment spending in the US economy is volatile as these factors can both work together to increase growth or pull in opposing directions. Unlike stable consumption, investment is subject to erratic fluctuations over short periods as shown in the annual rates of change from 1960 to 1995.