Some More Concepts

Equilibrium and Full Employment — Two Different Ideas

The equilibrium level of output that we have been discussing — the point where aggregate demand (AD) equals aggregate supply (Y) — does not automatically mean that everyone who wants a job has one. This is a crucial distinction.

Think of the economy's production function at the aggregate level. Given the quantities of other factors of production (land, capital, technology), the level of output determines how much labour is employed. But the output level that satisfies the AD = Y condition is determined by spending decisions, not by the desire of every worker to find work.

Full employment level of income is defined as that level of income at which all factors of production — labour, capital, land — are fully employed in the production process. It is a supply-side concept, representing the economy's maximum sustainable output given its resources.

The equilibrium reached at the point where Y equals AD does not, by itself, signify full employment. Equilibrium only means that if the economy is left to itself, the level of income will not change — even if there is significant unemployment. The system is stable at that point, but it may be stable at a level far below what the economy is capable of producing.

Deficient Demand and Excess Demand

The equilibrium level of output can be either less than or greater than the full employment level of output. Each case has a distinct cause and consequence.

Deficient demand occurs when the equilibrium level of output is less than the full employment level. The root cause is straightforward: aggregate demand is not high enough to employ all factors of production. In the long run, this situation leads to a decline in the general price level — deflationary pressure.

Excess demand occurs when the equilibrium level of output is greater than the full employment level. Here, aggregate demand exceeds the economy's capacity to produce at full employment. Since output cannot physically rise beyond full employment (in the short run), the excess spending chases the same quantity of goods, leading to a rise in the general price level — inflationary pressure.

The Effective Demand Principle

The textbook now brings together several assumptions to explain how output is actually determined in the short run.

At a particular price level, the final goods (product) market reaches equilibrium when aggregate demand for final goods equals aggregate supply of final goods. Aggregate demand for final goods consists of:

• Ex ante consumption
• Ex ante investment
• Government spending (and other components)

The rate at which ex ante consumption increases when income rises by one unit is the marginal propensity to consume (MPC).

For simplicity, the analysis makes two key assumptions over the short run:

1. The price of final goods is constant.
2. The rate of interest is constant.

Under these assumptions, the level of aggregate demand for final goods is determined. Furthermore, aggregate supply is assumed to be perfectly elastic at this constant price. This means firms are willing to supply any amount of output demanded at that price — they do not raise prices when demand increases.

An increase in autonomous spending (say, a rise in government expenditure or autonomous investment) causes aggregate output to increase by a larger amount through the multiplier process. Similarly, a decrease in autonomous spending causes output to fall by a multiplied amount.

Summary of Key Concepts Introduced

| Concept | Meaning |

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