In the previous chapter we looked at the effects of a change in price.  One of the consistent factors of our evaluation is that a change in price caused us to move up and down the supply and demand curves.  However, demand and supply does change.  It does not stay in the same place.  This chapter will look at factors that cause the supply and demand curves to move.  A shift in demand or supply is the same thing as a change in demand or supply.

Just as supply differs from demand so does changes in supply and demand.  It may be helpful to think of a supply and demand curve model in this manner.  Suppose that all the demanders are in one room and all the suppliers are in another room.  A negotiator walks between each room eliciting bids for goods until an agreed price and quantity is reached. Then something changes in one or both of the rooms.  The negotiator must once again take bids until an agreed upon price and quantity is reached.  This lecture focuses on what changes inside of each of these rooms.  We will first look at changing demand and then changing supply.