As shown in the previous section, it is difficult for us to obtain analytical analysis due to the complex expressions. Hence, we resort to numerical studies to give clear comparisons of the results. In this section, we first investigate the manufacturer’s pricing strategies and key outcomes under all the cases to provide firm-level suggestions. Sequentially, we discuss the subgame perfect Nash equilibrium (SPNE) for the announcement game, aiming to reveal the policy selection behaviors of the governments. The results contribute to give policy-setting implications. We also check the efficiency of each case and the key outcomes such as welfare and emission amount. Finally, we study whether a bilateral negotiation scheme can improve the social welfare of the two nations.
This parameter set can ensure positive prices, demands, profit for the manufacturer, and social welfare for the governments.
4.1. Equilibrium Outcomes of Subgames for the Manufacturer and Governments
In this subsection, we carry out comparisons among the four cases for the manufacturer with regard to its pricing and production strategies, profits and total emissions. We also give the equilibrium solutions for the two governments to investigate their specific policy-settings.
Under the benchmark parameter setting,
Table 2 summarizes the equilibrium outcomes under various environmental policy portfolios of the governments, i.e., bilateral, unilateral, or no policy cases. From
Table 2, we can obtain the following results.
For one thing, imposing an emission cap in the South pulls up the two prices, shrinks demands in both markets, decreases the total emission, and eventually leads to profit loss for the manufacturer. As mentioned, given an effectively strict emission cap, which directly lowers the total emission, the profit-seeking manufacturer would always decrease the emission quotas. The total emission limitation by the cap translates to a constraint of the total production output for the manufacturer, as unit emissions of the conventional and green manufacturing are exogenous constants. Therefore, compared with a cap-free situation where the manufacturer is free to produce and emit, the manufacturer is forced to comply with the given emission cap and reduce its total production output accordingly. Note that the emission quotas generated to the manufacturer can be regarded as a limited resource to be carefully distributed to the two operating productions. Different from a cap-free scenario, an emission cap scheme gives inadequate emission allowances to the manufacturer who is best to allocate less quotas to both productions in order to achieve profit maximization. As indicated by the comparisons in the case pair (, ) or (, ), the manufacturer reduces sales in both markets so that the demands decrease. Correspondingly, the manufacturer has to price higher the products at home and abroad to keep its profit margins. The profit for the manufacturer, consistent with common sense, decreases as the total production output declines.
For another example, enforcing a carbon tariff in the North exerts no impact on the domestic price and sales, but pulls up the foreign price, decreases exports to North, lowers the total emission, and the manufacturer’s profit. The carbon tariff, unlike the emission cap, which directly limits the total emission and production output, functions to add monetary burden to each unit of export from the South to the North. This dampens the manufacturer’s interest of exportation and eventually shrinks the amount of exports. With fewer products distributed in the North, the manufacturer needs to tag the products at a higher foreign price to keep its profit margin. Case pair comparison (, ) or () show that whether or not the North implements a carbon tariff does not unilaterally alter the manufacturer’s domestic price of the conventional products, or equivalently, demand in the local market. This suggests that the manufacturer’s best response to a carbon tariff enforcement is to constrain the negative impact on the foreign demand for the green products, while keeping domestic sales of the conventional products unaffected. As such, the manufacturer is able to at least keep profit from the local market and only suffer profit loss from exports. The corresponding domestic price stays independent to the policy selection of the North. The total emission amount, therefore, declines as total product quantity decreases.
Taking the no-policy scheme (
) as a reference case, we aim to investigate the respective impacts of the two unilateral cases, namely, cap-only (
) and tariff-only (
) scenarios. Results show that the emission cap and carbon tariff function differently on the manufacturer. It is easy to check that a cap-only backdrop leads to less total production output, compared with a tariff-only regulation. As shown in
Table 2, a no-policy environment allows the manufacturer to take a production allocation strategy
. When merely an emission cap comes into effect, that figure alters to
, revealing that the manufacturer has to lower both production quantities so as to comply with the cap policy. Specifically, the sales drops more in the South than in the North. The rationale behind this result is that given smaller emission quotas which pull down both volumes, the manufacturer prefers to cut to a greater extent the conventional output whose production process generates more emissions rather than the green manufacturing. In contrast, the tariff-only case gives rise to the product distribution of
. As discussed, the tariff policy will not influence the domestic sales, but merely decreases the exports. Despite that the emission cap shrinks the domestic demand greatly and pulls down the foreign sales, the manufacturer responses to tag the conventional products in the South with a higher price, that is,
under
compared with the domestic price
under
. Therefore, the manufacturer is able to reap more profit under a unilateral cap policy. In sum, compared with a tariff-only scheme, the manufacturer’s total production volumes and emission amount decline more under a cap-only case. Accordingly, the total emission under a cap-only situation is less than its counterpart with a tariff-only scheme. The manufacturer’s profit, on another front, is higher under an emission cap policy merely.
From the perspective of the North government, the carbon tariff rate steps up if both governments decide to ratify the policies, in comparison with a tariff-only case. As seen from Cases
(bilateral policy) and
(tariff-only policy), the equilibrium tariff rate rises from
to
if the South changes from a cap-free decision to an effective cap policy. As indicated in
Table 2, under a bilateral case compared with a tariff-only condition, the manufacturer would sell much fewer products in the South and also lower the sales in the North. Consequently, the consumer surplus in the North decreases. As the negative effect of emission cap is considerably significant, the decrements of Northern sales and consumer surplus become obvious. Under such conditions, the best response of the North whose social welfare sums up the consumer surplus and the tariff income is to raise the tariff rate which leads to a higher margin of each export.
The standpoint of South government shows that with an effective emission cap, the South would stick to a stricter cap policy if the North ratifies a carbon tariff. Note that, as mentioned above, implementing a carbon tariff in the North will not change the domestic price and sales quantity, but merely pulls down the foreign demand. As the consumer surplus and the manufacturer’s domestic revenue are not affected, the South only needs to make a trade-off between the manufacturer’s profit from exports and the environmental damage. Our result shows that the South’s welfare-maximizing response is to tighten the emission cap so as to mitigate the emission damage.
In summary, (1) both policies increase the foreign price, and decrease exports amount, the manufacturer’s revenue, and total emission; (2) the emission cap negatively affects the domestic sales and pulls up the price in the South, however, the carbon tariff does not alter the price and product volumes in the South; (3) compared with the carbon tariff, the emission cap exerts more significant impacts on the manufacturer’s total production output while enabling the manufacturer to suffer smaller profit losses; (4) the North should legislate a tougher tariff rate once the South decides to enforce an emission cap rather than a cap-free option, and the South is advised to implement a stricter emission cap if the North moves from a tariff-free policy to a carbon tariff scheme.
4.2. Policy Selections in the Announcement Game
Until now, we have used numerical studies to derive the equilibrium solution in each subgame and make comparisons of the strategies for the manufacturer and the policy-setting for the regulators. In this subsection, we focus on the policy selections for the two welfare-maximizing governments who participate in an announcement game in the first stage. One major factor influencing the welfare of the governments points to the degree of emission damage, which is captured by parameter h. We search for the equilibrium policy selection (or the SPNE) for the two players under various values of h to measure the corresponding impacts. Besides, we introduce a negotiation scheme which is commonly seen in practice and theoretical researches to check if it is able to achieve welfare improvements for both players.
The impacts of emission damage on the Southern social welfare can be translated into multiple meanings [
27]. First, it spells how the South government weighs environmental damage in its social welfare. Second, it stands for the monetary losses for the manufacturer in terms of emission during its manufacturing processes. Third, it reflects the public concern in the South about emission issues. We also provide an additional explanation that interprets
h as the capability of the Southern environment to naturally absorb the carbon emitted by the manufacturer’s production activities. It is commonsense that different regions have various levels of ability to capture and decompose carbon pollution, due to the diverse geographic and environment characteristics. Therefore, we regard a higher
h as a less absorptive environment in the South to deal with carbon emission. In sum, a larger value of
h in the South stands for a greater weighting the government measures the emission damage in welfare, a larger amount of monetary lose for the manufacturer caused by emission, more green-sensitive consumers in the South, or a worse natural environment in terms of carbon absorption. In this subsection, we vary
to cover a broader range of emission damage, ceteris paribus in the benchmark setting. The reason is twofold: first, although the weighting values of other contributors in Southern welfare are normalized to 1, as shown in welfare function (
3), a greater value of
describes the fact that developing countries are increasingly emphasizing the importance of environmental protection and emission mitigation; second, instead of a fixed
, as in the benchmark set of parameters, varying the value of
h is able to better approximate the fact that different regions have various levels of public green awareness and natural absorption capabilities of carbon pollution.
Table 3 concludes the social welfare for the two governments under different policy selections in the announcement game. For each value of
h, there exists a unique equilibrium selection pair (SPNE). For clarity, we mark in each example the subgame equilibrium with an asterisk from now on.
One result reveals that if the environmental damage exerts relatively moderate social impact, e.g.,
, the social welfare of the South under the four cases is compared as
, and that of the North follows
. Under a comparatively moderate level of emission damage, the Southern welfare reaches its peak under the cap-only unilateral situation, whereas is the worst under a bilateral case. In contrast, the North enjoys highest well-being when the two governments choose a tariff-only scheme, and its lowest social welfare emerges if the South takes an emission cap but the North holds no tariff regulation. In general, each government would welcome a corresponding unilateral case where itself sticks to a policy and its partner gives up legislation.
Table 3 shows the equilibrium for the announcement game, which points to a cap-free and tariff-only scenario (Case
). Notice that the equilibrium case dominates the bilateral one in terms of each participant’s benefit. In other words, the equilibrium case
is Pareto-improving than the bilateral one for the two parties. Specifically, the North achieves its maximal welfare at the equilibrium among the four cases. Therefore, we conclude that the equilibrium of tariff-only scheme is satisfactory for both sides as the Northern social welfare peaks and the South is not the worst.
An interesting observation points to a switch of equilibrium case when the emission damage mounts to a more significant level, e.g.,
. As shown in the second and third rows in
Table 3, the equilibrium of the announcement game refers to the bilateral condition where both regulators implement their respective policy. It is easy to check that for the South, the welfare is compared as
, and the Northern welfare shows
. Such results reflect the policy selection from each government’s perspective. For the South, it is always better to ratify an emission cap, regardless of what the North’s choice is. That is, effectuating an emission cap is always a dominant decision for the South. The Southern benefit drops to the lowest if it gives up the cap while the North taxes exports. By the same token, the North is always wise to choose a carbon tariff, whether the South legislates an emission cap or not. The least-wanted case for the North is that no tariff is imposed but its partner implements an emission cap. Also, the no-policy scheme is the second-best for both regulators. Therefore, we conclude that the dominate strategy or policy for the South points to always enacting an emission cap, and the best move for the North is to insist a carbon tariff. As a result, both parties are wise enough to make policy selections according to best interest of themselves, which comes to the bilateral case.
However, notice that the case of no-policy (
) actually dominates the equilibrium bilateral one (
) in terms of social welfare for both sides. In other words, the two are able to achieve Pareto improvement of welfare if they both decide to announce no policy in the game. This leads to a prisoner’s dilemma for the participants of the announcement game. Besides,
Table 4 shows that the total welfare under the four cases follows the order
, indicating that the no-policy accomplishes a greatest efficiency of welfare, whereas the equilibrium case is least ideal. As a result, the two governments, although trying to make their respective best selection, miss the goal of reaching a satisfactory situation for both sides. We emphasize that such prisoner’s dilemma would emerge when the emission damage becomes relatively significant (that is,
). Also, note that we set our backdrop of the announcement game under a non-cooperative manner that the two players act simultaneously without collaboration or negotiation. In addition, comparing the total welfare under the four cases with that of the centralized case reflects the efficiency of each subgame. As seen, the efficiency decreases with increasing
h. This result emphasizes the importance of cooperation between the nations, since a greater environmental damage largely hinders the efficiency of all the non-cooperative subgames in terms of welfare.
From the perspective of emission abatement, we see from
Table 5 that total emission for the manufacturer is compared as
if the emission damage is severe; whereas
if the environmental impact is comparatively moderate. Notice that in the absence of an emission cap, the manufacturer’s total emission is not limited and thus is not impacted by the degree of emission damage. In other words, as shown in
Table 5, the emission under
and that under
remain independent to the change of
h. It is easy to check that the total emission is always highest under a no-policy situation and lowest when bilateral-policy emerges. Under a no-policy scheme, the manufacturer is neither limited by emission constraint nor burdened by tariff cost. Compared with other cases, this is a most lax regulation environment for the manufacturer who will gear up to carry out manufacturing activities and outputs at greatest production quantity. Along with peak product volumes, the total emission also mounts to a highest level. On the contrary, under a bilateral case where the manufacturer has to pay tariff for exports and is forced to obey the emission cap, the production volume is smallest among all cases, which leads to a least amount of emission for the manufacturer. When the emission damage is significant, the effect of cap on emission mitigation gets more obvious so that a unilateral cap policy cuts more emission than a tariff-only regulation does. If the environmental damage is measured to be relatively moderate, e.g.,
, the cap becomes less strict and the tariff exerts greater impacts on emission cut so that
holds.
As mentioned in
Section 3, there exist a variety of international environmental agreements in practice, under the framework of which several nations work together as cooperative partners to set the environmental policies [
4,
8,
28]. In a bid to investigate a possible way out of the prisoner’s dilemma, the two governments confront when the emission damage is significant, and we follow the Nash negotiation process as in optimization problem (
21).
Table 6 gives the equilibrium solutions under the original bilateral and the negotiation scenarios as well as the social welfare of the governments.
Table 7 replaces the proceeding bilateral case with the one after negotiation, aiming to check the possible impact of negotiation on the policy selections of the governments.
As shown in
Table 6, the tariff rate after negotiation largely drops from
to
, whereas the emission cap significantly jumps from
to
. Recall that in the preceding analysis, each government should tighten its policy if the partner determines to impose the respective policy. However, we show that the negotiation actually asks both sides to take a step back so as to ink a cooperation. Put differently, the South lifts up its emission cap and the North enforces light tariff. The two governments achieve a Pareto improvement, that is, a win–win situation in terms of welfare under the negotiation framework. Further, the negotiation not only enhances the benefits of both sides compared with the original bilateral case, but also enlarges the Northern welfare to an extent that outperforms that in the no-policy scheme, as indicated in
Table 7. Moreover, the efficiency of the bilateral case after negotiation increases to
, which approaches the highest efficiency (
under the no-policy scenario) among those of all the subgames. Besides, the total emission (
) is less than that under a no-policy condition (
). We conclude that the negotiation is able to help the governments out of the prisoner’s dilemma, achieve Pareto improvement in welfare and slightly mitigate total emission. This result serves to voice our theoretical supports to the prevalent application of international environmental cooperation.
To sum up, we conclude, first of all, that equilibrium policy selection of the governments depends on the degree of emission damage in the South: A moderate level of damage generates equilibrium of the unilateral tariff policy where the Northern welfare peaks and Southern well-being is not worst; a high level of damage leads to a prisoner’s dilemma as the two regulators would arrive at a bilateral-policy scenario, which is dominated by a no-policy scheme. Second, a negotiation between the two regulators is able to help out of the dilemma and achieve welfare Pareto-improvement.