損益分岐点

The break-even point occurs when total consumption equals total disposable income. At this precise moment, every dollar earned is spent with nothing saved or borrowed. It represents the threshold where an individual or economy transitions between dissaving and saving behavior, marking a critical equilibrium state.

The break-even point appears where the consumption function intersects a 45-degree line drawn from the origin. This 45-degree line represents all points where disposable income equals consumption. The intersection marks the exact income level at which consumption and income are equal, visible in the Keynesian Cross diagram.

When consumption exceeds disposable income, an individual operates below the break-even point and must either borrow money or use accumulated savings to cover the shortfall. This unsustainable situation cannot continue indefinitely without external financial support or depletion of existing assets and reserves.

When income exceeds consumption, an individual operates above the break-even point and has surplus funds available for saving. This surplus represents the portion of disposable income not spent on current consumption and can be allocated to investment or future use, contributing to national saving.

The break-even point helps policymakers determine when consumer behavior shifts from dissaving to saving and forecast effects of taxation or interest rate changes on aggregate demand. In recessions, increasing national income beyond the break-even point stimulates saving and investment, promoting long-term economic growth and stability.

The consumption function expresses the relationship between aggregate consumption and national income through the equation C = a + bY. The break-even point occurs where C = Y, meaning the entire output produced is consumed with zero aggregate saving, revealing critical insights into the relationship between income consumption and saving.

Autonomous consumption represents expenditures that occur regardless of income level, shown as the 'a' component in the consumption function. It shifts the consumption function vertically on a graph, which moves the break-even point to a higher income level. Higher autonomous consumption requires greater income to reach equilibrium where consumption equals disposable income.