Benchmarking covariates balancing methods, a simulation study

Abstract: Causal inference in observational studies has advanced significantly since Rosenbaum and Rubin introduced propensity score methods. Inverse probability of treatment weighting (IPTW) is widely used to handle confounding bias. However, newer methods, such as energy balancing (EB), kernel optimal matching (KOM), and covariate balancing propensity score by tailored loss function (TLF), offer model-free or non-parametric alternatives. Despite these developments, guidance remains limited in selecting the most suitable method for treatment effect estimation in practical applications. This study compares IPTW with EB, KOM, and TLF, focusing on their ability to estimate treatment effects since this is the primary objective in many applications. Monte Carlo simulations are used to assess the ability of these balancing methods combined with different estimators to evaluate average treatment effect. We compare these methods across a range of scenarios varying sample size, level of confusion, and proportion of treated. In our simulation, we observe no significant advantages in using EB, KOM, or TLF methods over IPTW. Moreover, these recent methods make obtaining confidence intervals with nominal coverage difficult. We also compare the methods on the PROBITsim dataset and get results similar to those of our simulations.