["The Manchester School, Volume 94, Issue 3, Page 329-340, June 2026. ", "\nABSTRACT\nThis paper assesses the sustainability of Ireland's public debt to modified gross national income ratio since 1924 using a smooth transition autoregressive model. Empirical findings show that Ireland's debt has historically been mean reverting, exhibiting both non‐linear and asymmetric behaviour. The speed of adjustment was highest during two brief periods, centred around 1990 and 2016, characterised by simultaneous growth in nominal income and reductions in public debt.\n"]