This thesis is composed of three independent chapters in applied microeconomics. The first chapter studies the effect of interest groups on legislative voting. Using the alphabetic allocation of seats in the European Parliament, we show that former employees of interest groups influence the voting behavior of their colleagues when sitting together. When the subject of the vote is relevant to the interest group, the probability that nearby colleagues cast the same ballot increases by 2.4 percent, and that of abstention decreases by 9 percent, while no effect is detected for other vote subjects. These probabilities increase for votes about budgetary allocations, being comparable to those of sitting beside motion leaders. Revolving doors are problematic for the political process also when working in reverse.The second chapter studies gender differences in early occupational choices: Empirical evidence shows that men and women hold different types of occupations. It is however difficult to disentangle the channels via which these differences come about because observed equilibrium outcomes arise from preferences of agents on both sides of the market, and search and matching frictions. This paper relies on a unique labour market setting allowing us to isolate the supply side factors driving gender-based occupational segregation. We find that supply-side factors are important. Female and male medical students facing the same choice set make drastically different occupational decisions, even at the top of the performance distribution. Women prefer occupations characterised by lower expected earnings and time requirements, less competition, and a higher social contribution. We also find evidence suggesting that when constrained in their choices, women have a stronger preference for the location in which they are going to live compared to their male counterparts. The third chapter studies the causal effects of welfare benefits supporting parents with low birth weight newborns on their subsequent fertility and the mother’s labor market decision. I exploit the discontinuities in the eligibility criteria that entitles parents of newborns with birth weights below certain thresholds to receive monetary payments to devote themselves to the care of their newborn child, fully funded social security contributions and information courses. Using Spanish birth register data, I find that these welfare benefits impacted both the extensive and intensive margin of the fertility decision of low socioeconomic households. Mothers in these households who have a newborn with a birth weight right below 1100 grams are on average 6 percentage points (19 percent) more likely to have a subsequent child compared to similar mothers with newborns right above that threshold. This effect is mostly coming from young mothers for whom the benefits are also found to substantially reduce the time to have the subsequent child. These mothers are also found to be 16 percentage points (27 percent) more likely to hold a job at the time of their subsequent birth. These effects are presumably coming through the increase in available resources that low socioeconomic status households can dedicate towards the care of their extremely low birth weight newborns.