Nobel Laureate Amartya Sen's work on gender inequality is of seminal importance. His work on the theory of the household represents the household not as an undifferentiated unit, but as a unit of cooperation as well as of inequality and internal discrimination. Along with his academic collaborator Jean Drze, Professor Sen proposed and popularised the concept of "missing women" - estimated to exceed 100 million round the world - which has given us a new way of understanding and mapping the problem.