Does currency denomination reverse the ageing–growth relationship?

Currency denomination of real GDP per capita reverses the ageing–growth coefficient sign in a panel of 81 Turkish provinces, 2009–2023 (N = 1,215). Province fixed-effects regressions using USD-denominated real income yield β = −0.297 (p < 0.001); local-currency deflation reverses this to +0.070 (p < 0.001). First-difference (+0.044) and between-province (+0.213) estimators corroborate the reversal. The mechanism is the lira’s 90% USD depreciation after 2017, creating a spurious common trend that province fixed effects cannot absorb. Driscoll–Kraay standard errors and an alternative ageing indicator (65+ population share) confirm the sign reversal across all specifications. Negative ageing–growth estimates from high-inflation economies may partly reflect this measurement artefact rather than genuine demographic drag.