Editing Supply and demand (section)

====Demand curve shifts====
{{Main|Demand curve}}
[[File:Supply-demand-right-shift-demand.svg|thumb|Right-shift of [[demand curve]] increases both price and quantity.]]
When consumers increase the quantity demanded ''at a given price'', it is referred to as an ''increase in demand''. Increased demand can be represented on the graph as the curve being shifted to the right. At each price point, a greater quantity is demanded, as from the initial curve {{math|''D''<sub>1</sub>}} to the new curve {{math|''D''<sub>2</sub>}}. In the diagram, this raises the equilibrium price from {{math|''P''<sub>1</sub>}} to the higher {{math|''P''<sub>2</sub>}}. This raises the equilibrium quantity from {{math|''Q''<sub>1</sub>}} to the higher {{math|''Q''<sub>2</sub>}}.  (A movement along the curve is described as a "change in the quantity demanded" to distinguish it from a "change in demand", that is, a shift of the curve.) The ''increase'' in demand has caused an increase in (equilibrium) quantity.  The increase in demand could come from changing tastes and fashions, incomes, price changes in complementary and substitute goods, market expectations, and number of buyers. This would cause the entire demand curve to shift changing the equilibrium price and quantity.  Note in the diagram that the shift of the demand curve, by causing a new equilibrium price to emerge, resulted in ''movement along'' the supply curve from the point {{math|(''Q''<sub>1</sub>, ''P''<sub>1</sub>)}} to the point {{math|(''Q''<sub>2</sub>, ''P''<sub>2</sub>)}}.

If the ''demand decreases'', then the opposite happens: a shift of the curve to the left. If the demand starts at {{math|''D''<sub>2</sub>}}, and ''decreases'' to {{math|''D''<sub>1</sub>}}, the equilibrium price will decrease, and the equilibrium quantity will also decrease. The quantity supplied at each price is the same as before the demand shift, reflecting the fact that the supply curve has not shifted; but the equilibrium quantity and price are different as a result of the change (shift) in demand.