Schlesinger, 13 July 2007–2 of 2
A Method to Determine the Contribution of Individual Policies to the
Net Effect of a Group of Policies
Michael Schlesinger
Climate Research Group
Department of Atmospheric Sciences
University of Illinois at Urbana-Champaign
schlesin@atmos.uiuc.edu
Let T be the net effect of N policies, and Ti the net effect absent policy i. We define the
‘gross contribution’ of policy i as
Ci = T − Ti , i =1,...,N , (1)
the sum of which is
S = Ci
i=1
NΣ
. (2)
If T > S, the interaction among the policies creates a net effect that is greater than the
sum of its gross contributions – hence the group of policies is ‘synergistic’. If T < S, the
interaction among the policies creates a net effect that is less than the sum of its gross
contributions – hence the group of policies is ‘antagonistic’. The latter characterizes the
group of policies being considered by Governor Blagojevich’s Climate Change Advisory
Group.
To account for the disparity between S and T, we define the ‘net contribution’ of
policy i as
C′ i = T
S
⎛
⎝
⎜
⎞
⎠
⎟ Ci , i =1,...,N (3)
such that their sum is equal to T,
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