ENThe results of structural estimates of the hybrid New Keynesian Phillips curve are used to calibrate a semistructural state-space model that is then used to estimate a time-varying NAIRU. In the first version, the NAIRU is estimated as a simple autoregressive process. In the second, the state equation is enriched by two exogenous variables: long-term unemployment rate and labor costs. The results show that very longterm unemployment plays a statistically significant role in the explanation of the NAIRU, but even so, the majority of the fluctuations of the estimated NAIRU are explained by the autoregressive process itself.