This article analyzes the source data used to prepare the GDP estimates and the GDI estimates according to a set of criteria that reflects the quality, the availability, and the use of the data. This analysis allows for a better understanding of the differences between the source data that underlie the GDP estimates and those that underlie the GDI estimates and illustrates how the incorporation of the increasingly detailed and comprehensive source data leads to revisions to the GDP estimates and to the GDI estimates.