$c_{\text{eff}}$ for 3d $\mathcal{N}=2$ theories

Based on the observed behavior of the superconformal index in three-dimensional $\mathcal{N}=2$ theories, we propose a quantity that can be considered as an analogue of the "effective central charge." We discuss the general properties of this quantity and ways of computing it in a variety of different theories, including simple Lagrangian theories as well as more interesting strongly coupled examples that come from 3d-3d correspondence.