Quantity supplied is the specific amount of a good producers are willing and able to sell at one given price during a certain period. In AP Micro, a price change moves you along the supply curve to a new quantity supplied, while a change in supply shifts the entire curve.
Quantity supplied is the amount of a good or service producers are willing and able to sell at one specific price. It's a single point on the supply curve, not the curve itself. When the price of the good changes, producers respond by offering more or less of it, and you slide along the existing supply curve to a new quantity supplied. The law of supply says this relationship is positive. Higher price, higher quantity supplied.
The "willing and able" part matters. A producer might want to sell 1,000 units at $5, but if they can't actually produce that many in the time period, quantity supplied is lower. That's also why quantity supplied is always tied to a time frame. The amount a farmer can supply next week (almost nothing extra) is very different from what they can supply next year (a whole new planting season). This time-sensitivity is exactly what price elasticity of supply (Topic 2.4) measures.
Quantity supplied is the building block of basically all of Unit 2. Equilibrium (LO 2.6.A) is literally defined as the price where quantity supplied equals quantity demanded, so the market clears with no shortage or surplus. Disequilibrium (LO 2.7.A) is defined by the gap between them. A surplus means quantity supplied exceeds quantity demanded at the current price, and a shortage means the reverse. Price elasticity of supply (LO 2.4.A) is calculated as the percentage change in quantity supplied divided by the percentage change in price. If you're fuzzy on what quantity supplied means, every formula and graph in Unit 2 gets harder. Get it right and the rest of the unit is mostly applying one clean idea over and over.
Keep studying AP Microeconomics Unit 2
Supply (Unit 2)
Supply is the whole menu of price-quantity combinations; quantity supplied is one item off that menu. A change in the good's own price changes quantity supplied (movement along the curve). A change in anything else, like input costs or technology, changes supply (the whole curve shifts). The AP exam tests this distinction constantly.
Price Elasticity of Supply (Unit 2)
Elasticity of supply asks how strongly quantity supplied reacts to a price change. The formula is percentage change in quantity supplied divided by percentage change in price. If the magnitude is greater than 1, supply is elastic; less than 1, inelastic; exactly 1, unit elastic. A perfectly inelastic (vertical) supply curve means quantity supplied doesn't budge no matter what the price does.
Market Equilibrium (Unit 2)
Equilibrium is the one price where quantity supplied and quantity demanded match. Above that price, quantity supplied outruns quantity demanded and a surplus piles up, pushing price down. Below it, a shortage pulls price up. Market forces are just quantity supplied and quantity demanded chasing each other toward balance.
Producer Surplus (Unit 2)
Producer surplus is the gap between the price sellers receive and the minimum they'd accept, summed across every unit actually sold. The quantity supplied at the market price sets the right-hand edge of that triangle on the graph, so changes in quantity supplied directly change the size of producer surplus you calculate.
Multiple-choice questions test quantity supplied in two main ways. First, the law of supply itself, like "what happens to quantity supplied when price increases?" (it rises, movement along the curve). Second, elasticity calculations and classifications, like identifying unit elastic supply as the case where the percentage change in quantity supplied equals the percentage change in price, or recognizing what a perfectly elastic or inelastic supply curve looks like. On FRQs, quantity supplied shows up inside graph work. The 2024 FRQ Q2 (market for Good X) and 2025 FRQ Q2 (market for rice in Rushland) both hand you a competitive market graph and ask you to find equilibrium, then show how a shock or a price control creates a gap between quantity supplied and quantity demanded. Labeling that gap correctly as a surplus or shortage, and shading the right consumer and producer surplus areas, is where the points are.
This is the most-tested vocabulary trap in Unit 2. Quantity supplied is one specific amount at one specific price, shown as a single point on the supply curve. Supply is the entire relationship between price and quantity, shown as the whole curve. A change in the good's own price changes quantity supplied (you move along the curve). A change in a determinant like input prices, technology, or the number of sellers changes supply (the curve shifts). If an MCQ says "the price of steel rises, what happens in the market for cars?" the answer involves a shift in supply, not a change in quantity supplied caused by the car's own price.
Quantity supplied is the specific amount producers are willing and able to sell at one given price in a given time period; it's a point on the supply curve, not the curve itself.
When the price of the good itself changes, quantity supplied changes and you move along the supply curve; when a determinant like input costs changes, the entire supply curve shifts.
The law of supply says price and quantity supplied move in the same direction, so a higher price means a higher quantity supplied.
Price elasticity of supply equals the percentage change in quantity supplied divided by the percentage change in price, with a magnitude of 1 separating elastic from inelastic.
At equilibrium, quantity supplied equals quantity demanded; a surplus means quantity supplied exceeds quantity demanded at the current price, and a shortage means the opposite.
On FRQs, the quantity supplied at the market price marks the boundary you use to calculate producer surplus areas on the graph.
Quantity supplied is the specific amount of a good producers are willing and able to sell at one particular price during a set time period. It corresponds to a single point on the supply curve and rises when price rises, per the law of supply.
No. A change in quantity supplied is a movement along the supply curve caused by a change in the good's own price. A change in supply is a shift of the entire curve caused by something else, like input prices, technology, or the number of sellers. AP graders and MCQ writers treat these as completely different answers.
Quantity supplied increases. Higher prices make production more profitable, so producers offer more units. On a graph, you move up and to the right along the same supply curve. The supply curve does not shift.
Price elasticity of supply equals the percentage change in quantity supplied divided by the percentage change in price. A magnitude above 1 means elastic, below 1 means inelastic, and exactly 1 means unit elastic, where the two percentage changes are equal.
A surplus exists when quantity supplied exceeds quantity demanded at the current price, which pushes price down. A shortage exists when quantity demanded exceeds quantity supplied, which pushes price up. Per the CED (MKT-4.B.1), these market forces drive price and quantity back toward equilibrium.
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