ABSTRACT Financial advice is fragmented and not living up to its potential. Despite 75+ years of coexistence, the lifecycle models stemming from Ramsey (1926), Fisher (1930), Modigliani and Brumberg (1954), Friedman (1957), Modigliani (1966), Samuelson (1969), Merton (1969, 1971, 1992), as well as others, and the single‐period optimization models of de Finetti (1940 2006), Roy (1952), Tobin (1958), and Markowitz (1952, 1959, 1987) have largely remained separate; let alone, have they been brought together in a meaningful way. This lack of connection is indicative of the current paradigm of disconnected piecemeal approaches that dominate financial planning and investing. Building on the insights of Samuelson (1969) and Fama (1970) and methods developed by Idzorek and Kaplan (2024), we link lifecycle models and mean–variance optimization models into a combined, integrated model. This model simultaneously provides unified financial planning associated with lifecycle finance with integrated portfolio recommendations from single‐period optimization models. We argue that the industry should move toward an interconnected, hybrid lifecycle net worth optimization model.
A 2025 study studied this question.