Figure 1.

Causal directed acyclic graph corresponding to target trial 1. For each surgeon, is operative volume during interval , L_k is a vector of covariates during (e.g., surgeon characteristics, average patient characteristics, average hospital characteristics, and mortality risk), is operative volume during (under full adherence to assignment), is the 90-day mortality risk of patients who underwent an operation during , and U is a vector of unmeasured covariates. Directed edges between , L_k, and are omitted for simplification.