Abstract
Data from a national sample of hospitals were used to explore reasons for improved in-hospital survival rate for coronary artery bypass graft (CABG) surgery between 1972 and 1982. Increases in annual volumes of surgery explain a large fraction of the decline in death rates. The residual can be attributed to improved techniques, experience, and other factors, even though more operations were done on older patients and women in 1982 than 1972.