Self-Enforcing Trade Agreements and Lobbying

By Kristy Buzard (Syracuse University)

Going back to the mid-1980s, the repeated prisoner’s dilemma has been used to model the absence of strong external enforcement mechanisms for trade agreements.[1] Cooperation is enforced by promises of future punishment for any deviation from the agreement, and the amount of cooperation that can be achieved depends on the severity of the chosen punishments. The strongest incentive-compatible punishment is often the grim trigger strategy in which all players play the static Nash equilibrium forever when any of them defects.

More recent work shows that grim trigger punishments can be improved upon in some circumstances. Jee-Hyeong Park, for instance, has demonstrated that the presence of asymmetric information and imperfect monitoring can make it more efficient to choose shorter punishments.[2] In a similar setting, Alberto Martin and Wouter Vergote show that retaliation — i.e. delayed punishment — dominates reciprocity.[3]

In a recent paper, I identify a different rationale for limiting punishments: endogenous politics.[4] This paper is the first to incorporate endogenous lobbying along the lines of the classic Grossman-Helpman “Protection for Sale” model — the standard model for endogenizing politics in trade policy — into a repeated-game setting. In place of a unitary government, this model has two branches of government who share policy-making power.[5] By endogenizing the political economy weights, one can address questions about the commitment value of trade agreements, and examine the implications of self-enforcement constraints for the design of trade agreements.

I assume that the social-welfare maximizing executives of two countries choose trade agreement tariffs that must then be implemented by politically-susceptible legislatures.[6] For simplicity, only the import-competing industry is represented by a lobby. The weight the legislature puts on the import-competing industry’s profits increases in lobbying effort, which can be thought of as including campaign contributions as well as broader measures of lobbying activity. The lobby will choose its effort level to optimally influence the legislature’s decisions about whether to abide by the trade agreement and how to set tariffs in the absence of an agreement. Assuming there is no uncertainty about the effect of lobbying effort on the outcome of the political process, the lobby either exerts the minimum effort needed to derail the agreement or exerts no effort at all. The executives maximize social welfare by choosing the lowest tariffs that make it unattractive for the lobbies to provoke the legislature to violate the trade agreement. There will thus be no trade disputes in equilibrium, but the out-of-equilibrium threat that a lobby might provoke one is crucial in determining the equilibrium trade agreement structure.

Adding a lobby to the usual repeated-game model adds a new constraint. The constraint on the legislature is loosened by an exogenous increase in the length of the punishment: defections become relatively more unattractive as the punishment becomes more severe as in the standard prisoner’s dilemma. However, the new constraint due to the presence of lobbying becomes tighter because the lobby prefers punishment periods. The higher tariffs during punishment periods give the lobby increased incentive to exert effort as the punishment lengthens. In the face of this heightened lobbying incentive, the executives must raise the trade agreement tariff to avoid a trade dispute.

The optimal Nash-reversion punishment strikes a balance between these two competing forces, so adding endogenous politics suggests an optimal length for punishments: it is  finite for most values of the political weighting function and can be derived directly from the players’ incentive constraints.[7] Shortening the punishment in models with uncertainty serves to increase welfare by minimizing time spent in punishment periods. Since there is no uncertainty in this model, the players remain in the cooperative state in all periods.[8] Here, social welfare improves because shorter punishments weaken the lobby’s incentive to exert effort and this allows the executives to reduce the trade agreement tariffs.

For a given punishment length, increases in the patience of the legislature mean the lobby must exert more effort to induce the legislature to endure the punishment. The executive can thus reduce trade agreement tariffs without fear that the agreement will be broken. Increases in the lobby’s patience and the lobby’s ability to influence the legislature (as measured by the political weighting function) work in the opposite direction: they allow the lobby to exert less effort to provoke a trade dispute, and therefore higher equilibrium trade agreement tariffs are necessary to avoid a dispute.

The optimal punishment length itself also depends on how readily special interests are able to influence the political process. If the lobby is weak, the optimal punishment converges to that of the model without a lobby: longer punishments are better because the key constraint is the legislature’s. As the lobby becomes more influential, the optimal punishment becomes shorter because the lobby’s incentive becomes more important. That the optimal length of punishments is a function of the influence of the lobbies reinforces the idea that endogenizing politics can be critically important for institutional design questions.


Bagwell, K., and R.W. Staiger, (2005); “Enforcement, Private Political Pressure, and the General Agreement on Tariffs and Trade/World Trade Organization Escape Clause.Journal of Legal Studies, 34(2): 471–513.

Buzard, K., (2017a); “Self-Enforcing Trade Agreements and Lobbying.Journal of International Economics, 108(1): 226–242.

Buzard, K., (2017b); “Trade Agreements in the Shadow of Lobbying.” Review of International Economics, 25(1): 21–43.

Dixit, A., (1987); “Strategic Aspects of Trade Policy.” in: T.F. Bewley (ed.), Advances in Economic Theory: Fifth World Congress. Cambridge University Press, pp. 329–362.

Maggi, G., and A. Rodríguez-Clare, (2007); “A Political-Economy Theory of Trade Agreements.” The American Economic Review, 97(4): 1374–1406.

Martin, A., and W. Vergote, (2008); “On the Role of Retaliation in Trade Agreements.” Journal of International Economics, 76(1): 61–77.

Milner, H.V., and B.P. Rosendorff, (1997); “Democratic Politics and International Trade Negotiations: Elections and Divided Government as Constraints on Trade Liberalization.” Journal of Conflict Resolution, 41(1): 117–146.

Park, J.-H., (2011); “Enforcing International Trade Agreements with Imperfect Private Monitoring.” Review of Economic Studies, 78(3): 1102–1134.


[1] See for example Dixit (1987).

[2] Park (2011).

[3] Martin and Vergote (2008).

[4] Buzard (2017a).

[5] This approach follows Milner and Rosendorff (1997).

[6] The model admits an interpretation in which the same branch of government both negotiates the trade agreement and decides on the applied tariff ex-post, and thus the one-shot game shares much in common with Maggi and Rodríguez-Clare (2007).

[7] In Park (2011), the finite punishment length is due to imperfect monitoring and/or uncertainty.

[8] In Buzard (2017b), I show how uncertainty can be incorporated into this model.