3D Business Cycle Phase Space: Multiplier-Accelerator Model

This scene runs the identical Samuelson multiplier-accelerator recurrence as the 2D chart, but instead of drawing output against time on a flat plane it traces a genuine 3D phase-space curve through time, output level and the rate of change of output. Because the underlying model is a linear second-order difference equation, that curve is not decoration — its winding radius and direction are the geometric signature of the equation's complex or real characteristic roots. A damped cycle spirals inward toward the gold equilibrium plane, a sustained cycle holds a steady spiral radius, and an explosive cycle spirals outward until the economy runs away, all directly visible as you orbit the camera around the trajectory and tune the marginal propensity to consume, the accelerator and government spending live.