In: Economics
11. Given the demand function of McDonald’s BigMac
Ln(Qm)= 3-1.5Ln(Pm)+0.4Ln(PA)+0.5Ln(Pw)+0.02Ln(I)
Qm: the demand of BigMac,
Pm: the price of BigMac,
PA: the price of Arby’s sandwich
Pw: the price of Whataburger.
I: Income
What’s the own price elasticity of BigMac? Write out the formula, calculate and interpret.
What’s the cross price elasticity of demand of BigMac with respect to the price of Arby’s sandwich? Write out the formula, calculate and interpret.
What’s the cross price elasticity of BigMac with respect to the price of Whataburger? Write out the formula, calculate and interpret.
What’s the income elasticity of BigMac? Write out the formula, calculate and interpret.
If the price of Arby’s sandwich is increased by 20% , the price of Whataburger is decreased by 10%, and Income is increased by 10%. What is the aggregate effect on the demand for BigMac?
11. The demand function is given as
.
The own price elasticity of BM can bestated as
. For
, we have
or
or
or
. Hence, the own price elasticity is -1.5, ie for a unit increase
in percent change in own price of BM, the quantity of BM decreases
by 1.5 percent, suggesting that BM's burger is not a giffen
good.
The cross price elasticity of BM demand with respect to Arby's
sandwich can be stated as
. For
, we have
or
or
or
. Hence, the corss price elasticity of BM with respect to A's
sandwich is 0.4, ie for a unit percentage increase in price of A's
sandwich, the BM's demand increase by 0.4 percent, suggesting that
BM's burger is a substitute to A's sandwich.
The cross price elasticity of BM's demand with respect to
Whataburger can be stated as
. For
, we have
or
or
or
. Hence, the crossprice elasticity of BM with respect to price of
Whataburger is 0.5, ie for a unit increase in percentage of price
of Whataburger burger, the quantity demanded of BM's burger
increases by 0.5 percent, suggesting that BM is a substitute of
Whataburger.
The income elasticity of BM can be stated as
. For
, we have
or
or
or
. Hence, the income elasticity of BM is 0.02, ie for a unit
increase in percentage of income, the demand for BM rises by 0.02%,
suggesting that BM is a normal good.
The total effect on BM's burger can be stated as for
, we have
or
or
; and for
is basically the percentage change in
, thus
(assuming no change in price of BM) or
or
, ie the demand for BM rises by 3.2%. It can be seen that the
change in percentage changes of the variables in this model if
multiplied by their respective elasticities and aggregaated, can
determine the total change in quantity.