Business cycle

Start with the single most important empirical fact about a modern economy: it does not grow smoothly. Over decades, real output rises, because productivity and population push a rising trend (M7.01). But around that trend the economy oscillates, sometimes gently and sometimes violently, in a pattern regular enough to have a name (the business cycle) and irregular enough that no one can reliably time it. An analyst who models a company as if demand grows 6% every year forever has already made the deepest possible error about the world the company lives in. Demand comes in waves, and the height and timing of the next wave is the weather your businesses sail in.

What are the four phases of the business cycle?

The cycle has four phases, and it is worth fixing them as a shape you can draw:

• Expansion (recovery → boom). Output, employment, incomes, credit, and profits all rise. Early in an expansion there is slack (idle factories, unemployed workers), so growth is non-inflationary: you can produce more without bidding up wages and prices. As the expansion matures, the slack is used up; the economy approaches full capacity; and further growth starts to show up as inflation rather than volume. This is the crucial internal logic: an expansion sows the seeds of its own end by running the economy hot enough to force the central bank to lean against it.
• Peak. The top of the cycle: the moment activity stops rising and begins to fall. In real time, nobody rings a bell; the peak is only identifiable well after it has passed (which is the whole problem with the leading, coincident and lagging indicators). At the peak, capacity is stretched, inflation is typically elevated, the central bank is typically tight, credit has typically been extended to weaker and weaker borrowers, and asset prices are typically high. The peak is where excess is maximal.
• Contraction (recession → bust). Output and employment fall. Firms cut production, lay off workers, and stop investing; households, fearing for their jobs, cut spending; credit tightens as lenders pull back and defaults rise. The mechanism is horribly self-reinforcing: one firm's spending is another's income, so a cut in one place becomes a fall in income somewhere else, which becomes another cut (the paradox of thrift, and the reason recessions have momentum). A recession is the ordinary version; a depression is a recession that is deep and long, usually because a credit/debt collapse and a policy failure turned a downturn into a spiral (see the 1929 crash).
• Trough. The bottom: the moment activity stops falling and begins to rise, again identifiable only in hindsight. At the trough, the excess has been purged: inventories are lean, weak firms have failed, debt has been written down or paid down, the central bank has eased, and pessimism is maximal. Low expectations and cheap money set the stage for the next expansion, and the cycle turns.

Why does the business cycle happen?

Why does this happen at all? Three overlapping engines, in rough order of importance:

1. The credit cycle (the biggest engine; see the credit cycle). Credit is spending brought forward from the future (M7.01). When credit expands, spending exceeds income and the economy booms; when credit contracts, spending falls below income and it busts. Because credit can expand far faster than the underlying capacity to produce or repay, it overshoots in both directions. And because lending standards themselves loosen in good times and tighten in bad (Minsky), the credit engine is pro-cyclical: it amplifies rather than dampens. Most serious cycles are, at bottom, credit cycles.
2. The inventory (and investment) cycle. Firms hold inventory and build capacity based on expected demand. When demand surprises to the upside, they over-order and over-build (and their suppliers over-build to serve them, the bullwhip effect, where a small change in final demand becomes a large swing in orders up the chain); when demand disappoints, they slash orders and run inventories down, and the cut ripples up the supply chain magnified. This is the shorter, milder "inventory recession," and it is why the earliest sign of a turn shows up in new orders and purchasing-manager surveys (see the purchasing managers' index) long before it shows up in GDP.
3. External shocks. Oil-price spikes (1973, 1979, 1990, 2022), wars, pandemics (2020), and financial crises abroad (1997–98) can knock an economy off its path regardless of where the domestic credit cycle stood. Shocks do not follow a schedule and cannot be forecast, which is part of why the cycle cannot be reliably timed.

Hold one framing tightly, because it structures everything that follows: the cycle is fundamentally a story about credit and confidence expanding until they cannot, and then contracting until the excess is purged. The leading, coincident and lagging indicators are ways to locate yourself in that story; Minsky (the credit cycle) explains its engine; the case studies (seven cycles and crises) are the story told seven times with different costumes.