This dissertation contributes to the field of health economics, which, in the past couple of decades, has substantially increased our understanding of the determinants of human health, health-related behavior, and health care choices. A large body of literature has documented the influence of peer group behavior on individual choices. The purpose of my research is to examine the extent of such a phenomenon in breast cancer preventive behavior. Using Behavioral Risk Factors Surveillance System (BRFSS) surveys from 1993-2008, I measured the effect of other female screening behavior on an individual's decision to have a routine breast cancer screening by calculating the size of a so called social multiplier in mammography. I estimated a vector of social multipliers in the use of annual mammograms by taking the ratio of group-level effects of exogenous explanatory variables to individual-level effects of the same variables. Peer groups are defined as same-aged women living in the same geographical area: county or state. Several econometric methods were used to analyze the effect of social interactions on decision to undergo mammography, including ordinary least squares, fixed effects, the split sample instrumental variable approach, and a falsification test. My results supported the hypothesis that social interactions have an impact on the decision to have a mammogram. For all women over age 40, I found strong evidence of social interactions being associated with individual's education and ethnicity. In addition, the decision for women ages 40-49 to have a screening was subject to peer influence through their place of employment and ownership of health insurance. Finally, for women age 75 and older, being married and aging were the most important channels through which peer group influenced the decision to have a mammogram. This research has important policy implications in the presence of current health care reform that reimburses breast cancer screening at 100%, while rates of mammography receipt remain below the policy goal. Furthermore, I examined the effect of the 2009 United States Preventive Services Task Force change in screening recommendations on screening behavior. I demonstrated an immediate reduction in the receipt of mammography among women of all age groups following the revision of screening guidelines. I found that in 2010, the twelve month mammography receipt decreased by 1.97 (women ages 40-49), 2.20 (ages 50-74), and 3.61 (age 75 and older) percentage points, and the twenty-four months mammography receipt decreased by 1.47 (women ages 40-49), 1.05 (ages 50-74), and 1.92 (age 75 and older) percentage points. Analysis using a two-year follow up period after the revision of screening recommendations provided further support to this conclusion.

This dissertation develops a theoretical model of educational peer effects and then empirically tests whether or not they exist. In the theoretical model, each student selects an effort level to maximize utility; this effort choice depends on his peer group's effort and race. The students' equilibrium effort expression results in hypotheses that can be directly investigated empirically, a definition of the social multiplier, and conditions under which a social multiplier exists. The empirical model uses student-level data with observations on complete classrooms and two measures of effort, self-assessed effort and time spent studying, to investigate whether or not peer effects exist. The estimation results of the empirical model, interpreted using a simulation-based technique, find a positive relationship between the amount of time a student spends studying and time spent studying by peers who share his race; for self-assessed effort, the results are ambiguous. Simulations of policy experiments show that effort is higher in more racially homogeneous classrooms and that a social multiplier exists for both a reduction in the time a student spends working at a part time job and an increase in the student's socioeconomic status. / Economics

Il lavoro tratta gli effetti delle interazioni sociali tra compagni di scuola o di classe (c.d. peer effects) sugli apprendimenti degli studenti delle scuole medie. Il periodo di frequenza della scuola media rappresenta un momento critico nello sviluppo dell’adolescente che passa molto tempo con i compagni (a scuola e fuori da scuola) determinando forti legami di amicizia che ne influenzano lo sviluppo. Nel primo e nel secondo capitolo si tratta dell’effetto delle interazioni sociali tra studenti nativi e non nativi sull’apprendimento. Il terzo capitolo analizza il comportamento di cheating durante gli esami ufficiali come una forma di collaborazione che scaturisce da interazioni sociali. Il lavoro contribuisce alla letteratura esistente identificando gli effetti delle interazioni sociali con metodi innovativi e fornendo un’interpretazione stilizzata dei risultati mediante semplici modelli teorici. La tesi utilizza una banca dati innovativa che unisce i risultati dei test Invalsi in matematica e italiano (Esame Finale del I Ciclo, e Programma di Valutazione Nazionale, a.s. 2007-08, 2008-09, 2010-11), a dati amministrativi sulle scuole e dati censuari sulla popolazione (Censimento 2001). I risultati mostrano che le interazioni sociali influenzano in maniera significativa i risultati scolastici degli studenti. / I focus on social interactions among junior high school students attending the same class or the same school. Junior high school is generally considered by educational psychologists as the period in which friendships ties are usually formed and interactions with school mates take a relevant part of students’ time at school and outside school. In first and in the second chapter I focus on the effect on attainment of social interactions between native and non-native students. The third chapter deals with students’ cheating as a form of social interaction among classmates taking an official exam. The thesis contributes to the existing literature in proposing different empirical strategy to identify social interactions parameters and linking the results to stylized theoretical frameworks to shed light on the possible social mechanisms driving the estimated effects. The three chapters exploit rich and newly available datasets combining test score results in Math and Language from INVALSI (First Cycle Final Exam and National Evaluation Program, s.y. 2007-08, 2008-09, 2010-11), school administrative records, and the Italian Population Census Survey 2001. The results of the research demonstrate a strong role played by social interactions among school mates in affecting students’ attainment.