only one type of veto player. Many others exist as well, including an independent judiciary, an
independent central bank, federal and second legislative chambers, and the military.
We show that, ceteris paribus, increasing the number of veto players never increases and
usually reduces the range of agreements that would satisfy the countries involved in international
negotiations to form a PTA, thereby reducing the prospect of cooperation among them. We test
this claim by examining the domestic politics surrounding decisions to enter preferential
arrangements. Based on an analysis of all PTAs formed over the past fifty years, we find strong
statistical support for our argument. States are much less likely to enter a trade agreement as the
number of veto players increases.
Domestic Politics and Trade Agreements
Central to our argument is the view that domestic politics bears heavily on the prospects
of states entering a PTA. Thus, we depart from much of the work on international relations that
treats the state as a unitary actor. Instead, we view the state as an aggregation of actors with
varying preferences who share decision-making authority. More specifically, we focus on two
domestic political factors: the policy preferences of key actors and the institutions for power
sharing among them. The distribution of decision-making power among these actors and the
extent to which their preferences diverge define the number of veto players in a country.
Political institutions tend to define the relevant players in policy-making. The existence
of institutions for sharing decision-making power creates the potential for veto players. These
players are institutional or partisan actors whose assent is necessary to change existing policies
(Tsebelis 2002: 2). Tsebelis (2002) has shown that the difficulties of policy-making grow as the
number of veto players increases, as their preferences diverge, and as the internal coherence of
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Convention