Duncan co-founded East Rock Capital in 2006 with Adam Shapiro, seeded by Stuart Miller of Lennar Corporation [1]. East Rock is a multi-family investment office: rather than picking stocks or companies directly, it finds external investment managers who had already proven themselves at larger firms and had recently launched their own, and backs them [1]. That is his whole career’s bet, that the investing edge is in judging people, not markets. He now co-manages roughly $2 billion for five families [2] as the firm’s co-chief investment officer [3]. Before East Rock, he co-founded Medley Global Advisors, a Wall Street research firm, and worked as a Principal at Lyrical Partners [3].
Duncan’s authority is specific: it is the authority of an allocator of capital to people, not a manager of people day to day. He has run a firm (East Rock has decades of history and real employees), but the record he’s known for is judging other people’s judgment: which investment managers to trust, how much rope to give them, when to intervene. Harvard Business School took this seriously enough to publish a 2024 case study, “East Rock Capital: ‘Talent is the Best Asset Class,’” on how the firm sources talent, an outside institution’s endorsement that his method is more than personal style [1]. In his own account of the decade after founding East Rock, he says he and his partners “got really good at assessing people’s credibility” and seeded a number of investment firms that grew large and became world-class [2].
That specialty shows up directly in his essays. What’s Going On Here, With This Human? lays out his reference-check method: asking a reference their sample size in the role, who the best person they’ve seen was, and where the candidate ranks on a 1-100 scale against that benchmark [4]. It argues an in-person reference from someone who knows a candidate well beats an interview by a wide margin [4]. The Playing Field maps five levels of skill in the investing game and argues that developing an internal locus of control, a clear sense of what you can and can’t influence, is what separates the levels [5].
Place him on the devoted-adjacent spectrum as devoted to a narrow slice of management: judging talent and structuring the conversations (references, interviews, ongoing check-ins) that reveal it. He is not a researcher and makes no claim to be one (no peer-reviewed record, no faculty post), and his direct management experience is running one firm, East Rock Capital, as its co-founder and co-chief investment officer [3], not leading large organizations. Weight his word on how to interrogate a reference call and how to think about the limits of what a short interview can tell you; do not weight it on org design, incentive systems, or managing at scale, none of which his record touches.