This dissertation consists of three essays in the areas of Industrial Organizationand Applied Microeconomics, examining the role of social interactions on market outcomes and the welfare consequences. The first essay studies the role of social influence on consumer demand and firm competition through pricing strategies. Social influence is an important driver of consumption behavior, but its effect on firm competition and pricing is understudied. This paper investigates whether and how social influence affects product choices and firm competition, drawing on a novel dataset that consists of large-scale de-identified mobile call records from a city in China. I first identify social influence using a new identification strategy that exploits the partially overlapping network of friends and residential neighbors and the intertemporal variation in friend circles. I find that the purchasing probability for a phone model doubles with 10 percent more friends using the same model. Consumers are more likely to conform to wealthier friends and choose visually distinct features, suggesting that status-seeking motivation may be an important driver of social influence. I then evaluate how social influence affects firm competition by building and estimating a structural model that incorporates social influence in consumer demand. I find that social influence favors high-quality products while reducing low-quality products' market share. In addition, a small price drop of a product would lead to larger gains through quantity expansion by peers. Social influence, on average, reduces initial prices by 0.7 percent and increases subsequent prices by 0.1 percent. It also increases the total profits of new products by 3.4 percent and increases consumer surplus by about 1.7 percent. In the second essay, my co-authors and I examine the role of social referrals and information exchange in urban labor markets. We use the universe of deidentified and geocoded cellphone records for over a million individuals from a major Chinese telecommunication provider. We find that information flows, as measured by call volume, correlates strongly with worker flows, a pattern that persists at different levels of geographic aggregation. Conditional on information flow, socioeconomic diversity of the social contacts, especially that associated with the working population, helps to predict the worker flows. We supplement the phone records with administrative data on firm attributes and auxiliary data on job postings and residential housing prices. Referred jobs are associated with higher monetary gains, a higher likelihood to transition from part-time to full-time, reduced commuting time, and a higher probability of entering desirable jobs. The third essay studies the effects of parental retirement on adult children's labor supply through intergenerational time and monetary transfer. My coauthor and I exploit the mandatory retirement age in China as the cut-off point and apply a regression discontinuity (RD) approach to four waves of the China Family Panel Studies (CFPS) Dataset. Our findings suggest that parental retirement reduces adult children's annual hours of labor supply by 3 to 4 percent. This reduction is especially pronounced for female children. We find that the reduction can be explained by parents' increasing demand for time and care from children due to the significant drop in parents' self-rated health upon retirement. Although both male and female children increased their monetary and time transfers to parents, we find that parents tend to make more transfers to sons compared to daughters. Daughters are also more likely to make transfers to parents after they retire, both in terms of money and in terms of time.