In Marxian economics, the equation of aggregate demand with expenditure on GDP or GNP is rejected as false, on conceptual and statistical grounds.

Firstly, GDP as a measure of value added excludes purchases of all intermediate goods used up in production. Even so, gross value added cannot be simply equated with final demand, insofar as it excludes transfers and most trade in second-hand items.

Secondly, Gross Output from which GDP is derived by deducting intermediate expenditures, encompasses only those flows of income or expenditure regarded as related to production. Property income in the form of certain types of interest, transfers, land rents and realised capital gains from asset sales are excluded from gross output and GDP. Therefore, if the amount of property income (or transfers) increases, although GDP remains constant, national income receipts can nevertheless increase, and consequently aggregate demand can also increase.

Thirdly, Gross fixed capital formation measures only investment in productive fixed assets and does not constitute total investment, which includes also purchases of financial assets.

Fourthly, GDP in principle excludes sales of second-hand assets except for those modified by some prior productive activity (e.g. reconditioned cars).

Finally, expenditure on GDP obviously disregards the creation of credit money by banks and governments, which boosts aggregate demand.

Thus, it is argued, the catch-all Keynesian notion of aggregate demand:

obscures the distribution of income between social classes with different propensities to save, consume and invest, and

fails to differentiate appropriately between different kinds of investment and consumption expenditure.

Restraining consumption and a higher savings rate does not automatically imply more investment, and lower investment does not automatically mean higher consumption expenditure. Funds may (as Keynes himself acknowledges) be hoarded.