<div>This dissertation consists of three chapters. The first chapter, Inertia and Switching in Health Insurance Plans, seeks to examine health insurance choice of families and individuals employed by a large Midwestern public university during the years 2012-2016. A growing number of studies indicate that consumers do not understand the basics of health insurance, make inefficient plan choices, and may hesitate to switch plans even when it is optimal to do so. In this study, I identify what are later defined as unanticipated, exogenous health shocks in the health insurance claims data, in order to examine their effect on families' plan choice and switching behavior. Observing switches into relatively generous plans after a shock is indicative of adverse selection. Adverse retention and inertia, on the other hand, may be present if people remain in the relatively less generous plans after experiencing a shock. The results could help inform the policy-makers about consumer cost-effectiveness in plan choice over time.</div><div> Physicians’ relationships with the pharmaceutical industry have recently come under public scrutiny, particularly in the context of opioid drug prescribing. The second chapter, Pharmaceutical Opioid Marketing and Physician Prescribing Behavior, examines the effect of doctor-industry marketing interactions on subsequent prescribing patterns of opioids using linked Medicare Part D and Open Payments data for the years 2014-2017. Results indicate that both the number and the dollar value of marketing visits increase physicians’ patented opioid claims. Furthermore, direct-to-physician marketing of safer abuse-deterrent formulations of opioids is the primary driver of positive and persistent spillovers on the prescribing of less safe generic opioids - a result that may be driven by insurance coverage policies. These findings suggest that pharmaceutical marketing efforts may have unintended public health implications.</div><div> The third chapter, Accountable Care Organizations and Physician Antibiotic Prescribing Behavior, examines the effects of Accountable Care Organizations (ACOs). Physician accountable care organization affiliation has been found to reduce cost and improve quality across metrics that are directly measured by the ACO shared savings program. However, little is known about potential spillover effects from this program onto non-measured physician behavior such as antibiotic over-prescribing. Using a two-part structural selection model that accounts for selection into treatment (ACO group), and non-treatment (control group), this chapter compares physician/nurse antibiotic prescribing across these groups with adjustment for geographic, physician, patient and institutional characteristics. Heterogeneous treatment responses across specialties are also estimated. The findings indicate that ACO affiliation helps reduce antibiotic prescribing by 23.9 prescriptions (about 19.4 percent) per year. The treatment effects are found to vary with specialty with internal medicine physicians experiencing an average decrease of 19 percent, family and general practice physicians a decrease of 16 percent, and nurse practitioners a reduction of 12.5 percent in their antibiotic prescribing per year. In terms of selection into treatment, the failure to account for selection on physician unobservable characteristics results in an understating of the average treatment effects. In assessing the impact of programs, such as the ACO Shared Savings Program, which act to augment how physicians interact with each other and their patients, it is important to account for spillover effects. As an example of such spillover effect - this study finds that ACO affiliation has had a measurable impact on physician antibiotic prescribing.</div>