This paper discusses empirical comparisons of higher education institutions across world regions. It argues that institutional data systems have the potential for complementing global comparisons promoted by rankings by providing sensible information on institutional size, budgets, staffing, enrolments and activity profiles. With this perspective in hand, this paper tackles three questions. First, how is it feasible to identify Higher Education Institutions (HEIs) given their complex structures? Second, how is it feasible to define the perimeter of HEI sectors? Third, what kinds of data could be used for comparison, and where are the main data gaps? By analysing institutional data systems across the United States, Europe and Asia, the paper concludes that institutional data systems display some remarkable similarities that make them an important resource for global comparisons; however, variation in the context of data production and usage implies differences in the higher education perimeter and on institutional delimitation; sensible comparisons, therefore, require explicit knowledge of the institutional context in which data have been borne.