emergence of new information can trigger positive responses in all these coun-
tries.18
This model can also be used to motivate why countries initially do not reduce
(or reduce as if costs of further reductions are high). Assume that for
ρo ∈ [0,ρ] a country will not engage in any reduction efforts. A reason for this
could be that as long as costs are believed to be high with a high probability,
then the IG will have almost full discretion over national policy (the marginal
gain from pressure from the IG is relatively high). Consequently, the IG will
put sufficiently high pressure against national reductions such that this country
acts as a high cost country.19 Importantly, though, as long as the government
has no incentives to become informed, which is the case as long as its estimates
of others’ responses are not sufficiently high, we know from section that the
decision makers have good incentives to accept claims (e.g. from home indus-
try) that costs are high. When a government has a pretty clear picture of the
costs, then it needs an extremely high effort from the IG to change this picture.
The chain of arguments goes as follows: Initially, the country holds a prior be-
lief about its own costs and others’ costs and the pressure from the IG to make
no reductions is relatively effective, since ρ < ρo. Now, the other country
makes a cost revealing move and costs are low. The higher the correlation of
costs, the more ‘informed’ the government becomes, and the less is the mar-
ginal effect of the pressure from the IG, in which case the pressure is reduced
and the national reduction is increased.
Finally, let us combine all the insights gained in this paper. Simply letting uni-
lateral actions be motivated by revelation of costs is not enough to get a satis-
factory explanation of unilateral actions. If reduction costs are correlated then
the transmission of information by use of a unilateral move makes sense. The
prospects of unilateral actions are enhanced if we re-model the determination of
policy choices. When such choices are made on the basis of messages received
18 This could, e.g., be the case for western democracies.
19 An example is the US policy on climate change issues, where the relatively high probability of
high costs has been given as the main reason against any reduction effort.
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