“NK models require fungible capital to avoid balance sheets — "
Non-fungible capital isn’t a hypothesis that needs testing — it’s the real-world condition.
Fungible capital is the modelling assumption, and once you drop it, balance sheets become unavoidable...
.. and the NK equilibrium story disappears.
Once capital is non-fungible, such exclusion is no longer valid, and New Keynesian models lose closure without explicit balance-sheet dynamics.
When demand shifts or prices change, firms can’t just move their capital to a better use. They’re left with assets that may no longer earn enough revenue — but the debts used to build those assets don’t disappear.
From Credit Creation to Claim Enforcement: Debt Service, Labour Share, and Balance-Sheet Constraints
"Macroeconomic models that omit leverage and debt service as state variables are therefore empirically incomplete for the purposes of analysing modern inflation and distribution dynamics in high-debt economies."
Services Inflation Dynamics, Housing Pass-Through, and the Misinterpretation of Wage Inflation
"In sum, services inflation in the United States is best understood as a housing-anchored, lag-driven process in which wages play an adaptive rather than causal role."