Jan 22 Flashcards
actual values of the various categories of expenditure
Ca
Ia
Ga
(Xa - IMa)
desired values of various categories of expenditure
same as actual values but without the a subscript
C: desired consumption
I: desired investment
G: desired gov purchases
X - IM: desired net exports
what does “desired” actually mean?
isn’t a list of what consumers and firms would buy if they had no constraints on their spending - it’s much more realistic
reflects what consumers and firms would like to purchase, given their REAL-WORLD CONSTRAINTS of income and market prices
what’s aggregate expenditure (AE)?
the sum of DESIRED or PLANNED SPENDING on DOMESTIC OUTPUT
by households, firms, governments and foreigners
AE equation
AE = C + I + G + (X - IM)
autonomous expenditures
elements of expenditure that don’t change systematically with national income
induced expenditures
any component of expenditure that’s systematically related to national income
assumptions of simplest short-run macro model
- no trade - closed economy
- no government - no taxes
- price level is constant
AE = C + I
what’s AE in the simplest macro model?
AE = C + I
in the simplest model, what mostly determines consumption?
disposable income (YD)
disposable income
YD
amount of income households receive AFTER DEDUCTING TAXES and ADDING TRANSFERS
2 possible uses of disposable income
- consumption (C)
- saving (S)
graph plotting per capita disposable income and per capita consumption
lines have steadily increased in tandem since the 1950s
the distance between real per capita disposable income and real per capita consumption is real per capita savings
in 2020 (pandemic) they started to diverge: disposable income increased and consumption decreased, meaning savings got larger
4 key factors influencing desired consumption
- disposable income
- wealth
- interest rates
- expectations about future income
equation for the simplest consumption function
C = a + b x YD
slope of the simple consumption function is less…
less than 1
it’s positive (because increase in YD leads to increase in C)
but less than 1 because most individuals want to save a fraction of each additional dollar they make
(if the slope equalled 1, people would be spending each dollar they made)
consumption function: what does the 45 degree line indicate?
at this level, all the disposable income possessed by households will be consumed
reference point we can use to determine if people are saving or not saving at each level of income
consumption function graph: where’s the break even level of income?
point where the consumption function intersects the 45 degree line
equation for the slope of the consumption function
b = change in C / change in YD
if you have the consumption function, you automatically have…
the savings function
because out of disposable income, everything that you don’t consume you end up saving
so if:
C = 30 + 0.8 YD
then
S = -30 + 0.2 YD
marginal propensity to consume (MPC)
MPC relates the change in desired consumption to the change in disposable income that brings it about
MPC = change in consumption / change in YD
MPC is the ______ of the ______ _______
slope of the consumption function
average propensity to consume (APC)
equal to total consumption divided by total disposable income
APC = C / YD
as the level of income rises, what happens to the APC?
it falls
because APC = C / YD