How should central banks optimally aggregate sectoral inﬂation rates in the presence of imperfect labor mobility across sectors? We study this issue in a two-sector New-Keynesian model and show that a lower degree of sectoral labor mobility, ceteris paribus, increases the optimal weight on inﬂation in a sector that would otherwise receive a lower weight. We analytically and numerically ﬁnd that, with limited labor mobility, adjustment to asymmetric shocks cannot fully occur through the reallocation of labor, thus putting more pressure on wages, causing ineﬃcient movements in relative prices, and creating scope for central bank’s intervention. These ﬁndings challenge standard central banks’ practice of computing sectoral inﬂation weights based solely on sector size, and unveil a signiﬁcant role for the degree of sectoral labor mobility to play in the optimal computation. In an extended estimated model of the U.S. economy, featuring customary frictions and shocks, the estimated inﬂation weights imply a decrease in welfare up to 10 percent relative to the case of optimal weights.