总需求曲线

The aggregate demand curve slopes downward because as the overall price level rises, the total quantity of real output demanded decreases. This inverse relationship occurs through three mechanisms: the real balances effect reduces purchasing power, the interest rate effect raises borrowing costs, and the net export effect makes domestic goods more expensive for foreign buyers while imports become relatively cheaper.

The real balances effect occurs when prices rise, causing the value of money holdings to fall. Households lose purchasing power and reduce spending. This decline in consumption directly decreases the total quantity of real output demanded in the economy, contributing to the downward slope of the aggregate demand curve.

When the overall price level rises, people need more money to purchase high-cost items like homes or cars. Lenders have limited funds in the short run, so interest rates rise. Higher borrowing costs reduce overall spending in the economy, lowering aggregate demand and reinforcing the downward slope of the demand curve.

Aggregate demand consists of four main components: consumption spending by households on everyday items, investment spending by businesses on tools and machines, government spending on public services, and net exports, which is the value of goods sold to other countries minus goods bought from them. Together, these form total spending in the economy.

When domestic prices rise, goods from that country become more expensive for foreign buyers, while foreign goods become relatively cheaper. As a result, exports fall and imports rise, reducing net exports. This decrease in net exports lowers total aggregate demand, contributing to the downward slope of the curve.

When government spending increases on services like building schools or roads, it raises total aggregate demand in the economy. Government spending is one of the four main components of aggregate demand, so increases in this component directly boost overall spending and economic demand.

Aggregate demand falls when the price level increases because households and firms have less purchasing power and face higher borrowing costs. The real balances effect, interest rate effect, and net export effect all work together to reduce total spending on goods and services, causing the quantity of real output demanded to decrease.