lobby for regulatory congruence across states. Our seed lobby strength results from table 3 (List
2 and 4) suggest this latter scenario, i.e., base state’s relatively strong seed lobby favors
regulatory congruence. Evidence of such activity can be found in the Recommended Uniform
State Seed Law by the Association of American Seed Control Officials, which outlines common
procedures for labeling, complaint, and dispute settlement in seed certification and trade across
states. The American Seed Trade Association and the American Nursery and Landscape
Association also promote development of domestic seed and nursery-product markets and
address regulatory issues across states. So, it is likely that states with significant seed or nursery
production (e.g., Oregon, California) lobby for regulatory congruence across states.
Most coefficients on commodity producers’ lobby index are not significant in table 2
(1997) with List 4 being an exception. However, results for 2002 show a pattern similar to that
illustrated in figure 2 for List 1 and 3 (table 3). The other significant coefficients, one each in
List 2 and 4, have signs opposite of those shown in figure 2. Relating equation (3) to the results
from List 1 and 3, it appears that commodity producers’ gains from agronomic protection more
than offset the price-enhancement effect.
Statistical significance confirms stakeholders’ input, but does not provide information on
their relative importance. To infer on the latter, we use a variance decomposition approach from
Fields (2003). The variance of the dependent variable, regulatory congruence, is first
decomposed into that explained by the explanatory variables and the residual. In our case, the
explanatory variables including the fixed effects explained about 60 percent of the variance of
regulatory overlap in all four lists for 1997 and 2002. Of this 60 percent, the share of all 3 lobby
variables ranged from -6 to 9 percent in 2002, while the range for 1997 is 2 to 10 percent. The
rest is accounted by ecological and agronomic dissimilarities and state-specific effects.
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