Understanding the Optimum Tariff in International Trade

The question asks about the key characteristic of the optimum tariff. The optimum tariff is a tariff rate that a large country can impose to maximize its national welfare.

A large country, unlike a small country, can influence world prices by changing its trade volume. When a large country imposes a tariff, it reduces its demand for imports. This reduced demand can lower the world price of the imported good, thereby improving the imposing country's terms of trade (the ratio of its export prices to its import prices).

However, imposing a tariff also reduces the volume of trade. National welfare depends on the balance between the gain from improved terms of trade and the loss from reduced trade volume (due to the distortion of consumption and production decisions). The optimum tariff is the rate that achieves the best possible balance, leading to the highest level of national welfare.

Optimum Tariff and Offer Curves

The concept of the optimum tariff is often explained using offer curves. An offer curve shows the quantities of exports and imports a country is willing to trade at various terms of trade. When a country imposes a tariff, it shifts its effective terms of trade relative to the external terms of trade. The tariff-imposing country is essentially willing to offer less of its export good for a given amount of imports.

The optimum tariff allows the imposing country to move to the highest possible indifference curve on the trading partner's offer curve. The point where the imposing country's highest attainable indifference curve is tangent to the partner country's offer curve determines the optimum tariff rate and the new trade equilibrium.

Analyzing the Options

Let's evaluate each option:

• Option 1: Must occur in the elastic range of the tariff imposing home country's offer curve. This option focuses on the home country's offer curve elasticity. While offer curve elasticity is related to a country's willingness to trade at different prices, the determination of the optimum tariff hinges on the reaction of the *partner* country to the changed terms of trade induced by the tariff. The key is the partner's responsiveness.
• Option 2: Takes account of the probability that the partner country will retaliate with protective measures of its own. The standard theory of the optimum tariff is a 'beggar-thy-neighbor' policy that assumes the partner country does not retaliate. A more complex analysis considering retaliation leads to concepts like a tariff war or Nash equilibrium tariffs, which are different from the basic optimum tariff concept. So, the standard optimum tariff does not account for retaliation.
• Option 3: Maximises total export sales of the imposing country. The goal of an optimum tariff is to maximize national welfare, not total export sales. In fact, the tariff typically reduces the volume of trade, which would likely reduce total export sales compared to free trade, although it improves the terms of trade on the remaining trade.
• Option 4: Must occur in the elastic range of the partner country's offer curve. This is the correct explanation. For the imposing country to be able to improve its terms of trade by restricting trade (imposing a tariff), the partner country's offer curve must be elastic at the resulting trade equilibrium point. If the partner's offer curve were inelastic, a reduction in trade volume would lead to a less than proportionate decrease in the import price, potentially worsening the terms of trade or offering no improvement. An elastic partner offer curve means the partner is responsive to the price change, allowing the imposing country to shift the terms of trade in its favor. The optimum tariff rate is positive only if the partner's offer curve is elastic. The tangency point described above (highest indifference curve tangent to partner's offer curve) will always occur in the elastic portion of the partner's offer curve (or at the corner if the elasticity is infinite, representing a small country).

Therefore, the optimum tariff relies critically on the responsiveness of the trading partner, which is captured by the elasticity of the partner country's offer curve.

Revision Table: Key Optimum Tariff Concepts

Additional Information on Optimum Tariff and Trade Policy

While the optimum tariff can theoretically increase a large country's welfare, several factors limit its practical application and desirability:

• Retaliation: The most significant limitation is the likelihood that trading partners will retaliate with their own tariffs. This can lead to a trade war where all countries are worse off than under free trade.
• Information Requirements: Calculating the optimum tariff requires detailed knowledge of the partner country's offer curve (demand and supply elasticities), which is often difficult to obtain accurately.
• Global Welfare: An optimum tariff benefits the imposing country but harms the trading partner and reduces global welfare compared to free trade. It's a non-cooperative strategy.
• Domestic Politics: Tariffs can create winners and losers within the imposing country (e.g., benefiting import-competing industries while harming consumers and export industries).

Economists generally advocate for free trade or coordinated trade policies over unilateral optimum tariffs due to the risks of retaliation and the negative impact on global efficiency.