Answer:
we propose a new measure to understand policy connections between the states. For decades, diffusion scholars have relied on the largely untested assumption that contiguous states are more similar than noncontiguous states, despite evidence that similarity is more complex than geographic proximity. We use a unique survey of citizens’ perceptions of other states to construct a national network of similarity ties between the states. We apply this new measure with a data set of state policy adoptions in a dyadic and monadic event history analysis and find that similar state adoptions are a reliable predictor of policy innovation. We argue that perceived state similarity is a more complete measure of how states look to each other than contiguity.