Staggered Synthetic Control Estimation and Inference // Implements the Staggered Synthetic Control (SSC) method for estimating treatment effects in panel data with staggered adoption, as proposed by Cao, Lu, and Wu (2020) doi:10.48550/arXiv.1912.06320. Constructs synthetic control weights via constrained quadratic programming, estimates heterogeneous treatment effects and event-time average treatment effects on the treated (ATT), and provides placebo- in-time confidence intervals and p-values.