where M denotes medical care demand, measured by physician
visits and emergency room visits; Info indicates consumer health
information searching behavior; Ltrust is a binary variable measuring
the degree of patients’ distrust in physicians; X is a vector of
exogenous observable individual characteristics and county-level
physician characteristics; ε is the disturbance term. Demeaned
Ltrust is used to interact with Info, so that the coefficient, ˇ2, on the
interaction can reflect the substitution effect of consumer health
information on medical care use, while the coefficient ˇ1 on Info
indicates the average effect. As per the conceptual discussion, we
expect that ˇ1 > 0 and ˇ2 < 0.