Ex post

Also called: Actual, realised · Topic: Aggregate Demand, Income Determination and the Multiplier · NCERT: Class 12, Ch 4 "Determination of Income and Employment"

Meaning

Ex post (Latin for "after the event") is the actual or realised value of an economic variable, such as consumption, investment, saving or output. It is recorded after the period is over, as it appears in the accounts.

It matters because national-income data are always ex post. Ex post values also always balance, even when the economy is not in equilibrium. The gap between plans and actual results is what makes firms change their output.

• Formula: Ex post I = Ex ante (planned) I + Unplanned inventory change

Explanation

Ex post vs ex ante: two values of the same variable

• Ex ante (Latin for "before the event") is the planned or intended value.
• It is what households meant to consume.

• It is what firms meant to invest or produce.

• Ex post is what actually happened.

• National-income accounting uses C (consumption), I (investment) and GDP in this sense.

• The same word, such as "investment", can mean two different numbers in the same year. Always ask: planned or actual?

• Why Keynes needed this split: Keynes wrote The General Theory in 1936, after the Great Depression.
• Firms produce what they expect to sell. Their expectations are plans, so they are ex ante [4].
• Actual spending is recorded ex post.
• Prices are assumed fixed, and there are spare machines and workers. So when plans and results differ, output adjusts, not prices.

The balancing item: unplanned inventory change

• Inventory (stock) is output that has been produced but not sold, so it stays with the firm.
• Inventory investment is the change in stock during a period (closing stock − opening stock).
• It is a flow, measured over a period.

• The inventory itself is a stock, measured at a point in time.

• There are two kinds:

• Planned: the firm chooses to keep a buffer stock, for example before the festival season.

• Unplanned: actual sales are different from expected sales, so stock piles up or runs down without anyone choosing it.

• Ex post investment includes both kinds. This is why ex post values always balance.

• NCERT example:
• A producer plans to add ₹100 of goods to her stock. Ex ante I = ₹100.
• Demand rises without warning. She sells ₹30 out of her stock.
• Her stock rises by only ₹70. Ex post I = ₹70.
• ₹70 = ₹100 + (−₹30). The −₹30 is unplanned inventory investment.

Identity vs equilibrium

• Ex post identity: actual output ≡ actual C + actual I.
• The sign "≡" means "true by definition". The identity always holds.

• Unsold goods are counted inside ex post I as unplanned inventory investment.

• Equilibrium condition (ex ante): Y = Ā + cY

• Y = output or income.
• Ā = autonomous expenditure, meaning spending that does not depend on income (planned investment plus autonomous consumption).
• c = marginal propensity to consume (MPC), the share of each extra rupee of income that people spend (0 < c < 1).

• This condition holds only in equilibrium. Solving it gives Y = Ā / (1 − c), where 1/(1 − c) is the investment multiplier.

• Worked example: Ā = ₹50 crore, c = 0.8. Equilibrium Y = 50 / 0.2 = ₹250 crore.

	Output ₹300 crore	Output ₹200 crore	Output ₹250 crore
Planned demand (AD)	50 + 240 = ₹290 cr	50 + 160 = ₹210 cr	₹250 cr
Unplanned inventory	+₹10 cr (unsold)	−₹10 cr (stock run down)	0
Ex post C	₹240 cr	₹160 cr	₹200 cr
Ex post I	50 + 10 = ₹60 cr	50 − 10 = ₹40 cr	₹50 cr
Ex post C + I = Y?	✓ ₹300 cr	✓ ₹200 cr	✓ ₹250 cr
Next move	Firms cut output	Firms raise output	No change

(The table assumes autonomous consumption is zero, so all of Ā is planned investment.)

• Saving and investment follow the same rule:
• Ex post S ≡ ex post I always holds in a two-sector economy (households and firms only).
• At Y = ₹300 crore: S = 300 − 240 = ₹60 crore, and ex post I = ₹60 crore ✓.

• But planned I is only ₹50 crore. Planned S is greater than planned I, so income will fall.

• Rule to remember: in equilibrium, unplanned inventory change = 0, so ex ante = ex post.

In India

• MoSPI (Ministry of Statistics and Programme Implementation), through the NSO, publishes GDP tables. These are ex post records of what was actually spent and produced.
• Gross capital formation = gross fixed capital formation (GFCF) + change in stocks [3]. Valuables are now shown as a separate item [2].
• Producers' stocks cover raw materials, semi-finished goods and finished goods [3].
• MoSPI calls the inventory line "Changes in Stocks (CIS)". It is an ex post figure, with planned and unplanned changes counted together.
• Q1 (April–June) 2026-27, current prices, base year 2022-23, released 31 August 2026 [2]:

Item (Q1)	2025-26	2026-27	Share of GDP 2026-27
Changes in Stocks (CIS)	₹1,07,661 crore	₹1,31,305 crore	1.5%
GFCF	₹25,12,912 crore	₹30,26,274 crore	34.3%
Valuables	₹68,100 crore	₹90,825 crore	1.0%
Discrepancies	₹64,852 crore	−₹69,478 crore	−0.8%
GDP	₹80,00,192 crore	₹88,26,871 crore	100%

• At current prices, CIS grew 22.0% in Q1 2026-27 [2].
• At constant (2022-23) prices, CIS fell 13.9%, to ₹1,23,063 crore [2]. The difference shows how much price changes can affect this line.
• Limit: official data give only the total change in stocks. They do not split it into planned and unplanned parts. That split exists only in theory.

Don't confuse with

• Ex ante: this is the planned value. Ex ante C + I = Y holds only in equilibrium. Ex post C + I ≡ Y holds always.
• Equilibrium: the ex post identity holding does not mean the economy is in equilibrium. Equilibrium needs unplanned inventory change = 0.
• "Discrepancies" line in GDP tables: this is a statistical gap, because estimates from different data sources do not match exactly [2]. It is not unplanned inventory.
• Inventory (stock) vs inventory investment (flow): the stock is measured at a point in time. Inventory investment is the change in that stock over a period, and it can be negative.

Prelims Hooks

• National-income accounts record ex post values. Ex post = actual or realised. Ex ante = planned or intended.
• Ex post I = planned I + unplanned inventory change. NCERT example: ₹100 planned + (−₹30) unplanned = ₹70 actual.
• Trap: "C + I = Y holds only in equilibrium" is false for ex post values. Only the ex ante equality needs equilibrium.
• Ex post S ≡ ex post I always holds in a two-sector economy. Ex ante S = ex ante I holds only in equilibrium.
• Positive unplanned inventory → AD < output → firms cut output. Negative unplanned inventory → AD > output → firms raise output.
• MoSPI's Changes in Stocks (CIS) was 1.5% of GDP in Q1 2026-27 (current prices, base 2022-23) [2].

Mains Points

• Inventories as an early warning sign:
• Stock that rises without being planned signals weak demand before GDP falls.
• Rising unsold stock → firms cut production → jobs and incomes fall → demand falls further (the multiplier working in reverse).

• This is why policymakers should track quarterly CIS data together with business-expectation surveys [2].

• Why demand management works:

• When planned demand is lower than planned output, the economy can settle below full employment.
• Government spending or an RBI rate cut raises Ā → planned demand rises → firms clear their stocks and raise output.

• This links the ex ante/ex post idea to fiscal and monetary policy in GS-III.

• Reading ex post data with care:

• A rise in CIS can mean confident firms building stock (planned) or goods that did not sell (unplanned). GDP data cannot tell these apart.
• Two more things call for caution: the discrepancies line (−0.8% of GDP in Q1 2026-27), and CIS rising at current prices while falling at constant prices [2].
• Stable, predictable policy keeps firms' investment plans (ex ante) steady, so plans and outcomes stay closer together [4].

Related concepts

• Ex ante

Read more

• Ex ante vs ex post: plans, outcomes and unplanned inventories