The death of Alan Greenspan at age 100 on 22 June removes the last direct link to an era that reshaped central banking globally. His 19-year tenure at the Federal Reserve, spanning four presidencies, established two enduring but contested doctrines: the ‘Greenspan put’—an implicit guarantee that the Fed would cushion collapsing asset markets—and ‘Greenspeak’, a deliberately opaque communication style designed to preserve policy flexibility. The immediate effect is a sharpened focus on how his intellectual inheritance will influence the Federal Reserve under Kevin Warsh, President Trump’s nominee to lead the institution.

Greenspan’s operational rule was to avoid preemptively deflating financial bubbles, arguing that central banks could not reliably identify them, and instead to supply ample liquidity after a crash. This framework guided the response to the 1987 Black Monday crash, when a one-sentence pledge of liquidity calmed markets, and later shaped the handling of the dot-com bust. Viewed from Washington, the approach contributed to the ‘great moderation’—a long period of stable growth and low inflation—and cemented the Fed’s reputation as an independent technocracy. Yet the same doctrine also presided over the credit and housing bubble that burst in 2008, triggering the Great Recession. Greenspan himself later acknowledged an over-reliance on bankers’ self-interest, while analysts in London note that the slow rebuilding of interest rates after the dot-com crash encouraged the subsequent mortgage boom.

The legacy now converges on Warsh, who has signalled sympathy for Greenspan’s reluctance to prick bubbles and has extolled the virtues of allowing technology investment booms to run their course. However, Warsh has also criticised the extraordinary balance-sheet expansion used to mop up after 2008, which he argues over-inflated asset prices. This creates a potential asymmetry: a Fed less willing to intervene with large-scale asset purchases after a crash, effectively removing the ‘Greenspan put’ that markets have priced in for decades. Other elements of Greenspan’s record—his chairing of the 1982–83 commission that stabilised Social Security, and his later advocacy for strong intellectual property protections as a driver of American economic power—remain secondary in the current debate.

The next factual milestone is Warsh’s confirmation process and his first Federal Open Market Committee meetings, where his posture on asset prices and balance-sheet policy will be tested. The central question is whether the Fed will retain the asymmetric response pattern that defined the Greenspan years or shift to a more hands-off stance toward both market run-ups and downturns.