I am reading "Principles of Economics" by N. Gregory Mankiw.
Why doesn't the supply curve shift to the left in the following situation?
Why do producers respond to the surplus by cutting their prices?
Suppose first that the market price is above the equilibrium price, as in panel (a) of Figure 9. At a price of $5 per cone, the quantity of the good supplied (10 cones) exceeds the quantity demanded (4 cones). There is a surplus of the good: Producers are unable to sell all they want at the going price. A surplus is sometimes called a situation of excess supply. When there is a surplus in the ice-cream market, sellers of ice cream find their freezers increasingly full of ice cream they would like to sell but cannot. They respond to the surplus by cutting their prices. Falling prices, in turn, increase the quantity demanded and decrease the quantity supplied. These changes represent movements along the supply and demand curves, not shifts in the curves. Prices continue to fall until the market reaches the equilibrium.