The economy moves in one repeating shape: expansion (growing), peak (growth stops, at its highest point), contraction (shrinking), trough (the lowest point, and the turn back toward expansion). It is a loop, not a line; the arrow from trough always leads back to expansion.

Four indicator types are defined purely by their timing against that loop, never by which single statistic they happen to be. A leading indicator moves before the cycle turns, predicting a turn that has not happened yet; new building permits are the outline's own example. A lagging indicator only confirms a turn after it has already happened; the unemployment rate is the classic case, since employers are slow to cut staff and slow to rehire. A coincident indicator moves with the cycle in real time, industrial production being the outline's own example. An inflation indicator tracks the price level on its own separate axis, unrelated to cycle timing at all. The trap between the two most-tested categories is treating leading and lagging as roughly the same idea; they are opposites in timing, one predicts, the other only confirms, never both.

The same cycle sorts stocks into types. A cyclical stock rises and falls with the cycle itself, a company whose sales depend on consumer confidence, a luxury car maker being the clearest example. A defensive stock holds steady regardless of the phase, since demand for its product does not depend on the cycle, household food and utility providers being the outline's own example. A growth stock is valued for future earnings and reinvests rather than paying out now, a separate axis from cycle sensitivity entirely.

Two named theories compete over how to respond to a downturn. Keynesian theory favors active government spending and tax cuts to replace lost demand, fiscal policy as the main lever. Monetarist theory favors managing the money supply instead, with policy set by steady rules rather than discretionary intervention, the monetary lever instead of the fiscal one.