Causes of the short-term cycles (average duration = 52 months – as measured by the US National Bureau of Economic Research) are believed to be a combination of:
• alternate savings & spending patterns of consumers (consumer confidence theory); and
• alternate expansion & contraction patterns of business inventory (+ business capital investment).
The longer-term economic cycles are dependent on more fundamental forces (such as growth in labor force and productivity, capital investments, technological innovation, and long-term weather cycles).