Equilibrium occurs at the output level where the planned aggregate expenditure curve intersects the 45 Degree Line. At that point, the amount households, firms, and governments plan to spend matches the economy’s real output. This intersection provides a graphical way to determine national income in the Keynesian framework rather than treating output as predetermined.
A point above the 45 Degree Line indicates that planned aggregate expenditure exceeds the economy’s real output at that income level. A point below it indicates that planned spending is less than production. These gaps signal pressure for inventories and output to change, helping explain how the economy moves toward an expenditure-output intersection.
The line supplies a constant benchmark for comparing planned spending with real output across different income levels. By observing where the expenditure curve sits relative to that benchmark, analysts can identify mismatches between production and intended purchases. This makes the effects of changing spending plans easier to examine within national income determination and multiplier analysis.
First, place real output on the horizontal axis and planned aggregate expenditure on the vertical axis. Then draw the 45 Degree Line so both variables have equal values, and add the planned expenditure curve. The intersection marks equilibrium output. Comparing the two curves at other points reveals where spending plans differ from production.
Fiscal policy can be studied by examining how a change in government-related spending affects the planned aggregate expenditure curve and its intersection with the 45 Degree Line. A shifted intersection indicates a different equilibrium level of real output. The framework therefore connects fiscal policy decisions with short-run economic activity and multiplier effects.
The Keynesian cross shows the level of national income consistent with planned aggregate expenditure and real output. It also indicates whether current spending plans align with production or create pressure for adjustment. Because the framework focuses on short-run economic activity, it helps organize analysis of household, firm, and government spending in the economy.