R-O-T-T-E-N is a mnemonic for the six determinants of supply in AP Macroeconomics: Resource prices, Other goods' prices, Technology, Taxes and subsidies, Expectations of future prices, and Number of sellers. A change in any of these shifts the entire supply curve left or right.
R-O-T-T-E-N is a memory trick, not a formal economic theory. It packages the six determinants of supply from Topic 1.5 into one word so you can recall them under time pressure. The letters stand for Resource (input) prices, Other goods' prices (what else producers could make with the same resources), Technology, Taxes and subsidies, Expectations of future prices, and Number of sellers.
Here's the part that actually gets tested. Each of these factors shifts the entire supply curve. Cheaper inputs, better technology, a subsidy, or more sellers shift supply right (more supplied at every price). Pricier inputs, a new tax, or sellers leaving the market shift supply left. This lines up with EK MKT-2.D.1, which says factors like changes in input prices cause the market supply curve to shift. Notice what's NOT on the list. The price of the good itself never shifts supply. A price change just moves you along the existing curve, which is the law of supply (EK MKT-2.C.1) doing its thing.
R-O-T-T-E-N lives in Unit 1: Basic Economic Concepts, Topic 1.5 (Supply), and it directly supports learning objective 1.5.C, which asks you to explain the determinants of supply using graphs. It also sharpens your grasp of 1.5.A and 1.5.B, because knowing what does shift supply makes it crystal clear what doesn't (the good's own price). This shift-versus-movement distinction is one of the most common trap setups in Unit 1 multiple choice. And the payoff compounds later. The habit of asking "does this event shift the curve or move along it?" is exactly the reasoning you reuse when you shift short-run aggregate supply in Unit 3.
Keep studying AP® Macroeconomics Unit 1
Supply Curve (Unit 1)
R-O-T-T-E-N is the answer to the question "what moves this curve?" The law of supply gives you the upward slope; the six R-O-T-T-E-N factors tell you when the whole line picks up and slides left or right.
Market Equilibrium and Equilibrium Price (Unit 1)
A supply shift is step one of a two-step story. When a R-O-T-T-E-N factor shifts supply right, the curve crosses demand at a new point, so equilibrium price falls and quantity rises. Almost every supply question on the exam ends by asking what happens to price and quantity.
Elasticity of Supply (Unit 1)
Don't mix these up. R-O-T-T-E-N tells you the curve shifts; elasticity tells you how steep or flat the curve is, meaning how responsive quantity supplied is to a price change. One is about position, the other is about shape.
Short-Run Aggregate Supply (Unit 3)
The same logic scales up. When SRAS shifts in Unit 3, the usual culprits are resource prices (like wages or oil), technology, and taxes or subsidies, which are R-O-T-T-E-N letters applied to the whole economy instead of one market.
You'll never see the acronym "R-O-T-T-E-N" printed on the AP exam. It's a study tool. What you will see are scenario-based MCQs like "the price of an input used to produce good X rises; what happens in the market for X?" Your job is to recognize the R-O-T-T-E-N factor, shift supply the correct direction, and read off the new equilibrium price and quantity. The classic trap answer involves the good's own price, which moves you along the curve instead of shifting it. On FRQs, supply shifts usually show up inside a market graph you have to draw and label, often as the setup for an equilibrium or surplus/shortage question. No released FRQ uses the acronym itself, but the determinants behind it are core Unit 1 graphing material.
A change in any R-O-T-T-E-N factor is a change in supply, meaning the whole curve shifts. A change in the good's own price is a change in quantity supplied, meaning you slide along the fixed curve. Quick test: if the question mentions the price of the good itself, no shift happens. If it mentions inputs, technology, taxes, expectations, or sellers, the curve moves.
R-O-T-T-E-N stands for Resource prices, Other goods' prices, Technology, Taxes and subsidies, Expectations of future prices, and Number of sellers, the six determinants of supply in Topic 1.5.
A change in any R-O-T-T-E-N factor shifts the entire supply curve, while a change in the good's own price only causes a movement along the curve.
Lower input prices, better technology, subsidies, and more sellers shift supply right; higher input prices, taxes, and fewer sellers shift supply left.
After identifying the shift, finish the analysis at the new equilibrium: a rightward supply shift lowers equilibrium price and raises equilibrium quantity.
The same shift-the-curve logic returns in Unit 3, where resource prices and technology shift short-run aggregate supply.
It stands for the six determinants of supply: Resource prices, Other goods' prices, Technology, Taxes and subsidies, Expectations of future prices, and Number of sellers. Each one shifts the market supply curve when it changes.
No. A change in the good's own price causes a movement along the supply curve (a change in quantity supplied), not a shift. Only the R-O-T-T-E-N factors shift the curve itself, per EK MKT-2.D.1.
The acronym itself won't appear on the exam, but the six factors it represents are tested constantly in Unit 1. MCQs give you a scenario like a new production tax or a technology improvement and expect you to shift supply correctly and find the new equilibrium.
R-O-T-T-E-N factors determine where the supply curve sits (they shift its position), while elasticity of supply describes the curve's responsiveness, meaning how much quantity supplied changes when price changes. Shifters change position; elasticity describes shape.
Left. Higher resource prices raise production costs, so producers supply less at every price. On a graph, the supply curve shifts leftward, pushing equilibrium price up and equilibrium quantity down.
Connect this key term to the AP exam workflow: review the course, practice questions, and check related study tools.
Review units, study guides, and course resources.
Check this vocabulary in multiple-choice context.
Apply key concepts in written AP responses.
Estimate the exam score you are working toward.
Review the highest-yield facts before practice.
Put the full course together before test day.