* Multinomial regression analysis
mlogit policy_level i.IF_quartile i.publisher i.location i.subject, base(2) rrr

* Walt tests for independent variable
mlogtest, wald
mlogtest, wald set(2.IF_quartile 3.IF_quartile 4.IF_quartile)
mlogtest, wald set(2.location 3.location)
mlogtest, wald set(2.subject 3.subject 4.subject)

* Model fit statistics
quietly mlogit policy_level i.IF_quartile i.publisher i.location i.subject, b(2)
quietly fitstat, save
quietly mlogit policy_level i.IF_quartile i.publisher i.location i.subject i.location##i.subject, b(2)
fitstat, diff

* Figure 1
mlogit policy_level i.IF_quartile i.publisher i.location i.subject, b(2) rrr
margins IF_quartile, atmeans predict(outcome(1))
marginsplot, name(no_policy)
margins IF_quartile, atmeans predict(outcome(2))
marginsplot, name(weak_policy)
margins IF_quartile, atmeans predict(outcome(3))
marginsplot, name(strong_policy)
graph combine no_policy weak_policy strong_policy, ycommon col(1)

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