These two questions ask respondents
to indicate their agreement on a Likert scale (where 1 ¼ strongly
disagree, 2 ¼ somewhat disagree, 3 ¼ neither agree nor disagree,
4 ¼ somewhat agree, and 5 ¼ strongly agree) to the statements
“protecting threatened species is important to me” and “protecting
endangered species is important to me.” From these responses, a
series of dummy variables were created to indicate if a respondent
chose options 1, 2, 4, or 5.We interact each of these species concern
variables with POST in order to examine the possible impact of the
spill on the more specific measures of species concern, thus
yielding eight interaction terms. Additionally, because these variables
are ostensibly related to environmental concern, their inclusion
allows us to minimize any possible omitted variables bias.