AP Syllabus focus: ‘Shifts in labor demand or labor supply change the equilibrium wage and quantity of labor in the market.’
Labor markets coordinate firms’ hiring decisions and workers’ willingness to work. When labor demand or labor supply shifts, the market settles at a new equilibrium wage and quantity of labor, creating predictable changes in employment.
Core market model: wage and employment
In the market for labor, the “price” is the wage rate, and the “quantity” is workers hired (or hours worked). The equilibrium occurs where firms’ willingness to hire equals workers’ willingness to work at that wage.
A competitive labor market diagram with labor demand (downward sloping) and labor supply (upward sloping) intersecting at equilibrium (E). It also marks an above-equilibrium wage (creating excess supply/labor surplus) and a below-equilibrium wage (creating excess demand/labor shortage), reinforcing how disequilibrium wages generate pressure for adjustment. Source
Equilibrium wage and employment: the wage rate and quantity of labor where quantity of labor demanded equals quantity of labor supplied.
A shift changes the entire curve (not a movement along it), so equilibrium must adjust through wage changes, employment changes, or both.
= quantity of labor demanded at wage (workers or hours)
= quantity of labor supplied at wage (workers or hours)
Shortage and surplus as signals
When the wage is “wrong” (above or below equilibrium), the market creates pressure for wage adjustment.
Labor shortage / labor surplus: a shortage occurs when at the current wage; a surplus occurs when at the current wage.
A shortage tends to push wages up (firms compete for workers). A surplus tends to push wages down (workers compete for jobs), assuming flexible wages.
Market effects of shifting labor demand
A shift in labor demand means firms want to hire more or less labor at every wage.
A four-panel set of labor-market graphs illustrating how shifts in labor demand and labor supply change equilibrium wage and employment. Panels show: demand increase (wage and employment rise), demand decrease (both fall), supply increase (wage falls while employment rises), and supply decrease (wage rises while employment falls). This is a compact visual summary of the directional results your notes emphasize. Source
Increase in labor demand (demand shifts right)
Equilibrium wage: rises
Equilibrium quantity of labor (employment): rises
Market logic: at the original wage, a shortage forms; wages bid up until the shortage disappears.
Commonly, this pattern reflects improved conditions that make workers more valuable to firms, but for this subtopic, the key is the directional effect on and .
Decrease in labor demand (demand shifts left)
Equilibrium wage: falls
Equilibrium quantity of labor: falls
Market logic: at the original wage, a surplus forms; wages fall until the surplus disappears.
Market effects of shifting labor supply
A shift in labor supply means more or fewer workers (or hours) are offered at every wage.
Increase in labor supply (supply shifts right)
Equilibrium wage: falls
Equilibrium quantity of labor: rises
Market logic: at the original wage, a surplus forms; wages adjust downward, encouraging firms to hire more.
Decrease in labor supply (supply shifts left)
Equilibrium wage: rises
Equilibrium quantity of labor: falls
Market logic: at the original wage, a shortage forms; wages adjust upward, reducing quantity of labor demanded.
When both curves shift
If labor demand and labor supply shift simultaneously, one variable is typically ambiguous:
If both increase: employment rises, but wage may rise or fall depending on which shift is larger.
If both decrease: employment falls, but wage may rise or fall depending on relative shift size.
If demand increases while supply decreases: wage rises for sure; employment is ambiguous.
If demand decreases while supply increases: wage falls for sure; employment is ambiguous.
What determines “how much” and change?
The elasticity (steepness/flatness) of labor demand and supply affects how the adjustment is split:
More elastic curve → larger change in quantity of labor, smaller change in wage.
More inelastic curve → larger change in wage, smaller change in quantity of labor.
FAQ
A shift changes supply at every wage (new curve). A movement along happens when the wage itself changes, changing quantity supplied on the same curve.
The market may not reach equilibrium quickly. A fall in demand with sticky wages can create persistent surplus (unemployment); a rise in demand can create persistent shortages (vacancies).
Either, depending on the context. AP questions may treat labour as number of workers or total hours; interpret $L$ consistently with the prompt.
Because demand and supply changes push employment in opposite directions in some cases. The net effect depends on which curve shifts more (and by how much).
The side of the market that is more inelastic bears more of the adjustment in wages (larger wage change), while the more elastic side contributes more adjustment through employment (larger quantity change).
Practice Questions
(2 marks) Explain what happens to the equilibrium wage and quantity of labour when the labour supply curve shifts right, ceteris paribus.
Equilibrium wage falls (1)
Equilibrium quantity of labour rises (1)
(6 marks) A local labour market experiences a decrease in labour demand and an increase in labour supply. Using the labour market model, determine the direction of change in equilibrium wage and explain whether equilibrium employment is determinate.
Labour demand shifts left (stated) (1)
Labour supply shifts right (stated) (1)
Equilibrium wage falls (1)
Correct explanation using surplus/shortage logic at initial wage (1)
Equilibrium employment is ambiguous/indeterminate (1)
Explanation that relative shift sizes determine the net change in employment (1)
