Supply: the supply curve and what shifts it
Grade 12 Social Studies Worksheet
Circle the best answer.
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Gasoline prices and miles driven, each April (EIA and Federal Highway Administration via FRED, read Nov 14, 2026). Columns: Month, Retail price of regular gasoline a gallon, Miles traveled by all vehicles. April 2019, $2.798, 273.4 billion; April 2020, $1.841, 167.6 billion; April 2021, $2.858, 252.2 billion; April 2022, $4.109, 258.0 billion. Miles traveled is a rough stand-in for gasoline used; compare the same month in different years. In our words: if one curve shifts, price and quantity moving the same way point to a demand shift, and moving in opposite directions to a supply shift.
Ari compares April 2019 with April 2020. Which shift does the evidence fit best?
- A fall in supply: miles fell, and a supply fall is the usual cause of less driving
- A movement along demand: price fell, so buyers chose to drive less at the lower price
- A rise in supply: price fell, and a supply rise is the usual cause of a lower price
- A fall in demand: price fell 34 percent and miles driven fell 39 percent, moving the same way
Bo compares April 2021 with April 2022, when price rose 44 percent and miles rose 2 percent. Which statement is best supported?
- Neither curve shifted: the market moved along one curve to a higher price and a higher quantity
- Demand rose: price and miles moved together, though a small supply fall may be part of it
- Demand fell: price rose and miles driven hardly moved, so buyers held back this time around
- Supply fell: a 44 percent price rise is the sign of a fall in supply and of nothing else on the card
Esme must pick the claim that the table cannot support. Which claim is it?
- The April 2022 price rise was caused by a fall in the supply of gasoline
- Miles driven in April 2020 were about 39 percent below April 2019
- The April 2022 price was about 44 percent above the April 2021 price
- Miles driven in April 2022 were still below the April 2019 level
A writer says demand for gasoline is elastic, since price fell 34 percent and miles fell 39 percent in April 2020. Jun tests it. What is the verdict?
- Shown: a ratio above 1 means that each price cut raised driving by a larger percent each time
- Shown: miles fell by more than the price did, so buyers responded strongly to the lower price
- Not shown: a demand fall moved the market along supply, so the 39 to 34 ratio is about supply
- Not shown: elasticity of demand can be read just from changes in buyers' income
A market before any shift (example figures, made up for practice)
Price per unit Quantity demanded Quantity supplied $20 350 150 $25 300 200 $30 250 250 $35 200 300 $40 150 350 $45 100 400 Equilibrium is $30 and 250. A shift moves the quantity at every price by the stated amount. Use the new quantities to find the price at which demand equals supply.
A cost shock cuts supply by 100 at each price. Kira finds the new equilibrium. Which pair is right?
- $30 and 150: the price stays put and the quantity falls by the full 100 shift
- $35 and 300: the price rises $5 and the quantity rises 50, as in a demand shift
- $40 and 250: the price rises $10 while the quantity stays at its old level
- $35 and 200: the price rises $5 and the quantity falls 50
Demand rises by 100 at each price and supply falls by 100 at each price. Luz finds the new equilibrium. Which is right?
- $35 and 300: just the rise in demand counts, so price and quantity both rise
- $35 and 200: just the fall in supply counts, so price and quantity move as in a cost shock
- $40 and 250: the price rises $10 and the quantity is unchanged
- $40 and 350: the price rises $10 and the quantity rises by the 100 demand shift
A reporter says the price moved from $30 to $35, so supply must have fallen. Noah tests it with the table. What is the best reply?
- Right: a price of $35 shows supply fell, since sellers raise prices just when goods are scarce
- Right: both explanations give the same quantity, so supply is the likelier cause
- Wrong: a price above $30 means demand rose, since buyers drive prices up in a market
- Not necessarily: a demand rise of 100 also gives $35, with quantity up to 300, not 200
Two markets, each with a $1.00 tax on every unit sold (example figures, made up for practice)
Market Elasticity of demand (size) Elasticity of supply Rice 0.5 1.5 Concert tickets 2.0 0.5 In our words, for a small tax: buyers bear a share equal to the elasticity of supply divided by the sum of the two elasticities, and sellers bear the rest. The side that responds less to price bears more. This holds whoever is billed.
Pia applies the rule to the rice market. Which statement about the $1.00 tax is best supported?
- Buyers bear 25 percent, about $0.25: 0.5 divided by (1.5 + 0.5), the demand share
- Buyers bear 75 percent, about $0.75: 1.5 divided by (1.5 + 0.5)
- Each side bears half, about $0.50, because the tax is $1.00 on each unit sold
- Sellers bear 75 percent, about $0.75, because the law bills the sellers of rice
Ren applies the rule to concert tickets. Which statement about the $1.00 tax is best supported?
- Sellers bear about 20 percent, $0.20, because their supply is the less elastic side
- Buyers bear 25 percent, $0.25, because 0.5 divided by 2.0 is the buyers' share
- Sellers bear about 80 percent, $0.80, because buyers' share is 0.5 divided by (0.5 + 2.0)
- Buyers bear about 80 percent, $0.80, because buyers pay a tax in the end
A council member says taxing rice sellers protects shoppers. Zee tests the claim. What is the verdict?
- Not so: shoppers bear about 75 percent, $0.75 of each $1.00, whoever is billed
- Not so: shoppers bear the full $1.00, since rice is a necessity that each household must buy
- Right: with demand elasticity 0.5 shoppers cut back sharply and so pay $0.25 or less
- Right: sellers pay the tax, so shoppers pay $0.00 more at the register