Relying on a framework that synthesizes key guidelines concerning the methodology of measurement, this paper offers an assessment of indices currently used to study gender disparities on a global scale and sheds light on these unresolved questions; what do these indices with gender-differentiated data actually measure? and how valid are these indices?  The authors also spell out the stakes of research on measures disaggregated by gender, and an agenda for work geared to producing good cross-national gender-differentiated indices.