business cycle

If you tracked an economy's total output over many decades and drew it on a graph, the line would rise over time — economies tend to grow. But it would not rise smoothly. It would climb, stall, dip, and climb again, like a hiker on a long uphill trail who keeps speeding up and slowing down. Those recurring ups and downs around the long upward path are the business cycle: the economy's habit of alternating between good times and bad.

Economists describe the cycle in four phases. In an expansion, output, jobs, and incomes grow and optimism spreads. Eventually activity reaches a peak — the high point, where the economy is running hot and may be overstretched. Then comes the contraction or recession, when output falls, firms cut back, and unemployment rises, until the economy hits a trough — the low point. From there a recovery begins, and a new expansion grows out of it, starting the cycle over. The phases are real but irregular: cycles vary in length and depth, and there is no fixed clock telling you when the next turn will come.

The key insight is that this is about the short run swinging around a long-run trend, not about whether the economy grows at all. Over decades the trend points up thanks to better technology, more workers, and more capital; the cycle is the wobble on top of that climb. Understanding it matters because each phase calls for different worries — overheating and inflation near a peak, unemployment and weak demand near a trough — and because much of macroeconomic policy is the attempt to make the wobble smaller. A common error is to expect cycles to be regular or predictable like seasons; in practice their timing surprises even experts.