Book excerpt: In this dissertation, I study how centralized systems and platforms can improve their operational efficiency by taking into account the behavior of their users. To accomplish this, I combine two key elements: (1) understand users' behavior, and (2) identify sources of inefficiency and design solutions to address them. To better understand what drives user behavior, I combine techniques from behavioral operations and economics to derive models and hypotheses of how users make decisions. Then, I use tools from the econometrics literature to test these hypotheses and validate the proposed models. Finally, I combine this knowledge with tools from market design and operations to design and implement solutions that alleviate the inefficiencies identified in these markets. In the first chapter, I analyze the effect of increasing transparency in procurement platforms. The second chapter studies how the assortment composition and the history of past usage affect users' behavior in a two-sided market, and how we can take this into account to increase the number of matches generated. Finally, in the third chapter, I study the application behavior of students in the Chilean college admissions problem and propose an estimation procedure to account for their strategic behavior.