The aggregation of sectoral or regional Phillips curves yields an inflation–unemployment trade-off that is not vertical in the long run if there are mismatches between supply and demand in the regional or sectoral labor markets. This remains true even when the individual Phillips curves are all vertical. This result stems from variations in the slope of the individual short-run Phillips curves, rather than from changes to the equilibrium level of unemployment. It implies a role for the management of the distribution of demand over different sectors or regions, in order to minimize the natural rate of unemployment.