Coherence Half-Life (τ½) as a Structural Observable in Reinsurance

Reinsurance has optimized the measurement of loss, but remains structurally under-instrumented at the interfaces where losses originate. This paper introduces the coherence half-life (τ½) as a candidate structural observable designed to measure the persistence of alignment across these seams—pricing versus outcomes, claims versus legal environment, hazard versus exposure, and model assumptions versus realized experience. Using an implementable measurement protocol (τ½–T0), the paper shows that contraction in τ½ can become observable months before deterioration appears in traditional financial and actuarial metrics. This creates a measurable decision window in which structural instability is present but not yet reflected in pricing, reserves, or model outputs. Operationally, τ½ functions as an upstream diagnostic layer. Contraction in pricing-to-claims coherence may signal emerging underpricing before loss ratios deteriorate. Instability at the claims–legal seam may surface reserve pressure in advance of development. Model-to-reality divergence may be detectable prior to observable model failure. In each case, τ½ does not predict outcomes, but exposes structural drift at the point where it forms. Strategically, τ½ is positioned as infrastructure: a measurement layer that complements existing actuarial and risk frameworks by quantifying what they do not directly observe—the stability of coordination across systems. If validated prospectively, this implies a shift from reactive measurement of realized loss to direct observation of structural degradation upstream of financial impact. All findings are explicitly framed as testable hypotheses. The protocol is implementable on standard internal datasets without new infrastructure, enabling independent validation or falsification across carriers, lines, and time periods. If τ½ does not demonstrate consistent lead time, or exhibits unacceptable false-alarm rates, this will become evident under prospective evaluation. If validated, even partially, τ½ represents a new category of risk visibility: converting hidden structural state into a measurable signal across pricing, reserving, modeling, capital allocation, and exposure management. More broadly, the paper advances τ½ as a candidate cross-domain structural observable, motivating investigation into whether coherence decay—and its measurable half-life—exhibits invariant behavior across complex systems.