A shift of a demand curve to the right, all other things unchanged, will lead to an increase in equilibrium quantity supplied and an increase in equilibrium price. A shift of a demand curve to the left, all other things unchanged, will lead to a decrease in equilibrium quantity supplied and an increase in equilibrium price.
DEMAND WILL INCREASE
A movement along a demand curve can be caused by many factors such as changes in tastes, preferences or incomes. The effects of these movements will depend on which way the demand curve shifts.
A shift to the right means an increase in equilibrium quantity supplied and equilibrium price while a shift to the left means a decrease in both quantities supplied and prices. The change could also mean no effect at all depending on where it occurs between Qs and P.
When there are external forces causing changes in supply/demand (shifts) then we must take into account their impact when evaluating how those individual markets may react. For example, if labour costs rise significantly for certain goods, this might lead to higher production costs but not necessarily affect others.