(AZ) are 138.27, 124.50 and 30.30 days (of measurable precipitation), respectively. The percent
difference of precipitation between AL with AL, AL with AR, and AL with AZ are respectively
0.00, -0.10, and -0.78, which form the first three elements of the first row of the dissimilarity
matrix. The above indices shows that the precipitation in AL is more similar to that of AR than
AZ. The main diagonal elements of dissimilarity matrix are zero, while the off-diagonal
elements can take values between negative and positive infinity.
Indexes of Agronomic Dissimilarities (Aij-): We include two variables to represent a state’s
agronomic characteristics. The irrigated land share of total (state) cropland and the field crop
land share of total (state) crop land. Field crops included corn, wheat, barley, soybeans, other
grains and cotton. These data are obtained from the 2002 and 1997 Census of Agriculture,
National Agricultural Statistics Service (NASS), US Department of Agriculture. Again, a 48x48
matrix of dissimilarity indexes is constructed for each variable.
Indexes of Lobbying Dissimilarities (o'., ωsij, ω,m): To represent stakeholders’ interest in
NXW/NXWS regulation, we obtained data on campaign contributions in state politics (Institute
on Money in State Politics, www.followthemoney.org). Specifically, we obtained the number
and dollar amount of contributions made by industry and interest groups. From these data we
identify political contributions of agricultural producers within which we also have data on seed
producers’ contributions. Data on nursery industry’s lobby contributions had several missing
values, which when replaced by zero lead to infinite dissimilarity indexes. As noted in the
theory section, seed producers and nursery growers have similar interests, and therefore, we
combined contributions of seed producers and nursery growers into a single lobby variable. To
represent the consumer interest group, we use contributions from consumer and environment-
based groups under the ideology-oriented contributions to state politics. Thus, we created 2
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