or in population. It could also change as a result of the net effect
of changes in all of the independent variables occurring at once.
Some textbooks reserve the term change in quantity demanded
a movement along a demand curve, that is, a change in as a
result only of a change in p. They then use other words for a
change in caused by a change in the other variables in the
demand function. This usage is potentially confusing because it
gives the single variable more than one name.
Our usage, which corresponds to that in more advanced
treatments, avoids this confusion. We call quantity demanded
and refer to any change in as a change in quantity demanded
this usage it is correct to say that a movement along a demand
curve is a change in quantity demanded, but it is incorrect to say
that a change in quantity demanded can occur only because of
movement along a demand curve (because can change for
other reasons, for example, a ceteris paribus change in average
household income).
4. Similar to the way we treated quantity demanded in note 2, let
represent the quantity of a commodity supplied and
represent, respectively, producers’ goals, technology, the
product’s price, and the price of the ith input.
The supply function isQDQDQDQD
QDQDC,X,p,wiQS=S(C,X,p,wi), i= 1 , 2 ,...,m