Economic Collapse as a Threshold Phenomenon: Operationalizing a Memory-Dependent Fragility Index

This paper operationalizes the memory-dependent threshold framework introduced in Fragility as a Memory-Dependent System: Structural Overload and the Architecture of Threshold Regime Shift (Lim, 2026, Zenodo DOI: 10.5281/zenodo.18743819). Rather than modeling crises as exogenous shocks to equilibrium systems, the framework treats macroeconomic regime shifts as first-passage threshold events that occur when accumulated coordination strain exceeds structural capacity. Instability is therefore modeled as memory-dependent rather than contemporaneous. Using publicly available U.S. macro-financial data (FRED), this paper constructs a measurable collapse functional integrating standardized debt-service acceleration, credit spread dispersion, and inflation as a bounded release proxy. The functional is evaluated against historical NBER recession dates to assess whether measurable strain accumulation precedes regime transitions. The objective is not deterministic crisis prediction but empirical demonstration that accumulated structural strain is observable, persistent, and threshold-relevant. This paper constitutes Working Paper I of the Zenodo Macroeconomics Threshold Validation research program.