“…Mizik and Jacobson (2004) employed fixed-effects instrumental variable estimation to address both heterogeneity and endogeneity in physician response to direct-to-physician marketing activities. Finally, Manchanda (2005), Janakiraman, Dutta, Sismeiro, andStern (2008), and Janakiraman, Sismeiro, and Dutta (2009) used physician panel data to estimate an individual-level model of prescription choice within a therapeutic class. Although these studies did not investigate the evolving nature of the corresponding prescription and marketing mix series, these authors find significant differences across physicians in response to pharmaceutical detailing, in choice state-dependence, and in learning rates.…”