The Business Cycle: Trough, Expansion, Peak, Recession

What this means

Economic activity does not rise in a straight line. It rises, stalls, falls back, and rises again, and economists organize that pattern into the business cycleThe recurring sequence of recession, trough, expansion, and peak that an economy passes through over time.. The cycle has four named parts, and knowing them lets you describe any stretch of economic history precisely instead of vaguely.

Start at the top. A peakThe turning point at which economic activity stops rising and begins to decline; the end of an expansion. is the moment activity stops increasing. From the peak, the economy enters a recession: real GDP declines, and so typically do employment, income, and production. The decline continues until the economy reaches a troughThe turning point at which economic activity stops declining and begins to rise; the end of a recession., the lowest point of that downturn. From the trough, expansion begins. Activity rises, and it keeps rising until a new peak is reached, at which point the cycle starts over.

Two details trip people up. The first is that peak and trough are turning points, not verdicts. A peak is not the moment the economy is healthiest in absolute terms; because of long-run growth, a trough in one decade can involve more output than a peak two decades earlier. The peak is simply where the direction changed. The second is the word "cycle" itself. It suggests regularity, like a pendulum, and business cycles have nothing of the kind. Post-war U.S. expansions have ranged from about a year to more than a decade. The sequence repeats; the timing does not.

Layered underneath the cycle is the long-run growth trend, driven by investment in factories, equipment, technology, and in people's health, education, and training. A well-drawn business cycle diagram shows the wave oscillating around an upward-sloping trend line, not around a flat one. That single graphical choice encodes the most important fact about the whole topic: fluctuations happen on top of growth.

Why it matters

Being able to name where the economy sits in the cycle changes what a headline means to you. "Unemployment rose last month" reads very differently near a peak than it does near a trough, because near a trough it may be one of the last bad readings before conditions improve. Employment tends to be a lagging indicator, meaning it often keeps deteriorating for a while after the trough in output has passed.

The vocabulary is also load-bearing for anything you will read later about policy. Central bankers and legislators describe their actions in terms of the cycle: stimulus is discussed as a response to a downturn, and restraint is discussed as a response to an overheating expansion. Without the four turning-point terms, those debates are unreadable.

Try it

1. On unlined paper, draw axes. Label the horizontal axis "Time" and the vertical axis "Real GDP." Do not use numbers; this is a schematic.
2. Before drawing any wave, draw a straight dashed line rising from lower left to upper right. This is the long-run growth trend. Label it.
3. Now draw a smooth wave that oscillates above and below that trend line, completing at least one full cycle and starting into a second. The wave must end higher than it started.
4. Label the four required features: mark a peak at a local maximum, a trough at a local minimum, bracket the downward segment between peak and trough as "Recession," and bracket the upward segment between trough and the next peak as "Expansion."
5. Deliberately make your second expansion a different length from your first. In the margin, write one sentence explaining why unequal lengths are more realistic than equal ones.
6. Add a second panel below your graph, sharing the same time axis, and sketch what the unemployment rate would plausibly look like across the same cycle. It should move opposite to real GDP. Mark where unemployment peaks relative to where GDP troughs.
7. Now check your sketch against reality. Pull the quarterly real GDP series from FRED with NBER recession shading turned on, covering 1960 to the present. Find one recession where the shaded band is short and one where it is long.
8. Write three sentences comparing your schematic to the actual series. What does your idealized wave get right, and what does it smooth away that the real data shows?

Check yourself