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In macroeconomics, consumption, saving and investment are key aggregates that determine aggregate demand and national income. Keynes highlighted that consumption depends mainly on income and introduced the consumption function. Saving is the part of income not spent on consumption. Investment (especially planned investment) affects output and employment and can create multiplied changes in income through the multiplier process. This topic covers meanings, Keynesian concepts and major determinants with exam-friendly tables.
Consumption (C) is expenditure by households on goods and services for satisfying wants (food, clothing, education, transport, etc.).
Saving (S) is that part of income not spent on consumption.
(in a simple model without taxes)
Investment (I) is expenditure on capital goods that increase productive capacity (machinery, buildings, inventories). In macroeconomics we often focus on planned investment.
Keynes suggested a stable relationship between consumption and income: Where:
Basic relationship in a simple model: MPC + MPS = 1
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In macroeconomics, consumption, saving and investment are key aggregates that determine aggregate demand and national income. Keynes highlighted that consumption depends mainly on income and introduced the consumption function. Saving is the part of income not spent on consumption. Investment (especially planned investment) affects output and employment and can create multiplied changes in income through the multiplier process. This topic covers meanings, Keynesian concepts and major determinants with exam-friendly tables.
Consumption (C) is expenditure by households on goods and services for satisfying wants (food, clothing, education, transport, etc.).
Saving (S) is that part of income not spent on consumption.
(in a simple model without taxes)
Investment (I) is expenditure on capital goods that increase productive capacity (machinery, buildings, inventories). In macroeconomics we often focus on planned investment.
Keynes suggested a stable relationship between consumption and income: Where:
Basic relationship in a simple model: MPC + MPS = 1
Higher MPC means a larger multiplier effect, because more of additional income is spent and becomes someone else’s income.
From this topic
Determinants of consumption include:
(Any three determinants can be written.)
Determinants of saving include:
(Any three determinants can be written.)
Keynes explained that consumption is closely related to income. The consumption function shows the relationship between consumption (C) and income (Y). In its simple form it is written as:
C = a + bY
where a is autonomous consumption (minimum consumption even when income is zero) and b is the marginal propensity to consume (MPC), with 0 < b < 1.
Two important measures of consumption behavior are APC and MPC:
APC tells us what fraction of income is consumed at a particular income level, while MPC tells us how much consumption changes when income changes. Generally, as income rises, MPC is positive and less than 1, so consumption increases but not as fast as income.
Thus, the consumption function and propensities help in understanding aggregate demand and predicting how income changes affect consumption in the economy.