Q.Describe the adjustments that may take place in an economy when ex-ante savings are less than ex-ante investments.

When ex-ante (planned) savings fall short of ex-ante (planned) investment, the economy is not in equilibrium. Producers plan to invest more than households plan to save, creating an excess demand for goods.

This triggers the following adjustment mechanism. Firms find their inventories depleting faster than anticipated — unplanned inventory investment becomes negative. Since actual investment always equals actual saving (the accounting identity $I = S$ holds ex-post), the fall in inventories means actual investment drops below what was planned. As stocks run down, producers respond by raising output and employment in subsequent periods.

The rise in production increases national income. With higher income, households save more (since saving is a function of income). This process continues until actual saving rises to match the planned investment level, restoring equilibrium. At the new equilibrium, ex-ante saving equals ex-ante investment, and there is no further unplanned change in inventories. …

The Ex Ante–Ex Post Distinction

Before diving into the adjustment mechanism, we need to be clear about what "ex ante" and "ex post" mean. Ex ante refers to planned or intended magnitudes—what households intend to save and what firms plan to invest at the beginning of a period. Ex post refers to realized or actual magnitudes—what households did save and what firms did invest once the period is over, including any unintended changes.

In equilibrium, planned savings must equal planned investment: $S = I$. But during the adjustment process, when the economy is out of equilibrium, ex ante savings and ex ante investment can differ. The key insight is that ex post savings and ex post investment are always equal by accounting identity (because actual investment includes unintended inventory changes), but ex ante magnitudes need not be.

The Situation: Ex Ante Savings < Ex Ante Investment

When planned savings are less than planned investment, households want to consume more (save less) than firms want to invest. This creates an excess of aggregate demand over aggregate supply at the prevailing income level.

Think of it this way: if people plan to save ₹100 crore but firms plan to invest ₹150 crore, the total demand in the economy (consumption plus investment) exceeds what is being produced. Consumption demand is higher because savings are lower, and investment demand is also high. The economy cannot sustain this imbalance.

The Adjustment Process

The adjustment unfolds through changes in output and income, mediated by inventory movements.

Step 1: Inventory Depletion

Firms find that goods are flying off the shelves faster than anticipated. Actual sales exceed planned sales. To meet the higher-than-expected demand, firms draw down their inventories—stocks of unsold goods shrink. This unintended fall in inventories counts as negative unintended investment, so ex post investment falls short of what firms had planned.

Step 2: Production Response

Seeing inventories fall below desired levels, firms respond by increasing production. They hire more workers, run additional shifts, and expand output. As production rises, national income rises because income is generated in the production process (wages, profits, rents).

Step 3: Induced Saving

As income increases, households' savings increase too. Remember the consumption function: $C = \bar{C} + cY$, which implies the saving function $S = -\bar{C} + (1-c)Y$, where $(1-c)$ is the marginal propensity to save. Higher income automatically induces higher saving, even though the saving function itself hasn't shifted.

Step 4: Convergence to Equilibrium

This process continues—output expands, income rises, and savings rise—until planned savings catch up to planned investment. At that point, aggregate demand equals aggregate supply, inventories stabilize at their desired levels, and firms have no further incentive to change production. The economy settles at a new, higher equilibrium level of national income.