Provide an example of a policy that uses market-based allocation with both price and quantity considerations.

• A. Command-and-control regulation with fixed limits.
• B. Subsidies only.
• C. Simple taxes on outputs with no quantity constraints.
• D. Cap-and-trade with auctioned permits and price floor/ceiling; taxes with subsidies adjust price and quantity.

Answer: (D)

This item tests a policy that combines a quantity limit with a price mechanism, using market trading to allocate resources efficiently. Cap-and-trade does exactly that: a cap sets the total amount allowed (a quantity constraint) and firms receive or must hold permits to emit. Those permits can be bought and sold, so the price of emitting arises from supply and demand in the permit market. Adding a price floor or ceiling helps keep that price within a predictable range, improving stability for firms and policymakers. The idea can be augmented with taxes or subsidies to nudge both price and quantity toward desired targets, but the core is the blend of a hard quantity cap with a market-determined price.

The other options don’t fit this combination. A command-and-control approach fixes limits without creating a trading market, so there isn’t a price signal emerging from a market for allocations. Subsidies alone change the cost side but don’t impose an overall cap on quantity. A simple tax changes price but leaves quantity unconstrained, so there’s no mechanism to guarantee a specific total reduction.