Goodhart and Campbell converged independently because postwar technocratic governance created the conditions for their insight

Donald Campbell (social psychologist) and Charles Goodhart (monetary economist) independently formulated nearly identical laws about metrics losing value when used as targets. Campbell had slight priority (1974 vs 1975). Their convergence illustrates the adjacent possible: by the mid-1970s, decades of technocratic governance had made the insight almost inevitable.

Explanandum

Why did two scholars in completely different fields independently formulate the same fundamental insight about measurement and targets at almost exactly the same time?

Substance

Campbell’s formulations appeared slightly earlier — conference presentations in May and October 1974, with conceptual precursors to around 1969. Goodhart’s appeared in papers from a July 1975 Reserve Bank of Australia conference. Jeff Rodamar (2018) investigated the priority question and concluded Campbell was first.

The convergence isn’t coincidental. By the 1970s, postwar states had accumulated decades of experience governing through quantitative targets — Keynesian demand management, Soviet planning, McNamara’s systems analysis, British incomes policies. Enough time had passed for failures to become visible: stagflation defying the Phillips curve, body counts in Vietnam failing to track progress, monetary aggregates shifting their relationship to the real economy. The Lucas critique (1976) expressed the same insight for macroeconomic modelling. All three reached into the same adjacent possible from different starting positions.

The naming asymmetry is itself illustrative: “Goodhart’s Law” is better known than “Campbell’s Law” despite Campbell’s priority, because disciplinary prestige, pithiness of formulation, and citation networks distorted the attribution — a small instance of the phenomenon both laws describe.

Supports

• The Lucas critique (1976) expressed the same insight independently in macroeconomics — a “triple” discovery
• Rodamar (2018) establishes Campbell’s priority and the independence of the two formulations
• The 1970s were uniquely positioned: enough technocratic experience to generate failures, enough intellectual tools to articulate why

Challenges

• Convergent discovery may reflect shared intellectual climate (both read similar economics literature) rather than pure independent discovery
• The adjacent possible framing may be unfalsifiable — any simultaneous discovery can be explained post hoc as “the conditions were ripe”

Open Questions

• All three Works in Progress articles propose new metrics/mechanisms. What would Goodhart’s Law predict about their adoption as policy targets?
• Is there a way to design metrics that are robust to Goodharting, or is the phenomenon inherent in the relationship between measurement and intervention?

Source Context

Raised in discussion of whether Albrecht’s proposed Olley-Pakes metric would itself be Goodharted if adopted as a regulatory target. The convergent discovery question connected to the adjacent possible framework.