Sex selection through female feticide, infanticide, or neglect is an extreme manifestation of gender discrimination. Amartya Sen brought sex selection to public attention over 25 years ago when he famously claimed that 100 million women were “missing” in Asia. India has made tremendous economic progress since then, and we would expect this progress to be accompanied by greater gender equality. However, sex selection has intensified over time and spread throughout the country. Professor Munshi’s research provides an explanation for this disturbing phenomenon, which is based on the structure of the caste-based marriage institution in India and its interaction with economic development. The empirical evidence, based on new data, indicates that sex selection is not confined to a few castes (jatis) or a few districts, as commonly believed, but may be a more pervasive phenomenon among relatively wealthy households in all castes, with accompanying implications for the design of optimal policy.