Succession among the Nizari Ismaili Imams follows hereditary designation: the reigning Imam names his successor from among his male descendants, a choice not bound to primogeniture. The mid-twentieth-century succession illustrates the point: Aga Khan III bypassed his sons in 1957 in favor of his grandson, Prince Karim, citing in his will the need for a leader shaped by the conditions of the modern, technologically changing world, a rationale explicitly recorded rather than left to inference.
Since the mid twentieth century the Aga Khan has directed the Aga Khan Development Network, a large international network of agencies working in health, education, rural development, architecture and culture across Asia and Africa, an institutional expression of the Ismaili principle that the Imam's guidance addresses the material as well as the spiritual welfare of the community. This combination of hereditary religious authority with an extensive modern development bureaucracy is distinctive among the offices in this record, most of which separate spiritual leadership from large-scale international institution-building of this kind.
The Nizari Ismaili community today numbers in the low millions and is spread across South Asia, East Africa, Central Asia and diaspora communities in Europe and North America, a geographic breadth that follows historic trade and migration routes rather than any single national homeland. Unlike offices whose authority is bound to a single monastery, cathedral or state, the Nizari imamate is explicitly transnational, and the Imam's guidance to followers, known as firmans, is communicated directly to communities worldwide rather than mediated through a fixed territorial hierarchy of the kind found in several other lineage offices in this record.