  An improved and extended Bayesian synthetic control model is presented,
expanding upon the latent factor model in Tuomaala 2019. The changes we make
include 1) standardization of the data prior to model fit - which improves
efficiency and generalization across different data sets; 2) adding time
varying covariates; 3) adding the ability to have multiple treated units; 4)
fitting the latent factors within the Bayesian model; and, 5) a sparsity
inducing prior to automatically tune the number of latent factors. We
demonstrate the similarity of estimates to two traditional synthetic control
studies in Abadie, Diamond, and Hainmueller 2010 and Abadie, Diamond, and
Hainmueller 2015 and extend to multiple target series with a new example of
estimating digital website visitation from changes in data collection due to
digital privacy laws.
