One of the first to refine the idea of the epidemiological transition was Preston, who in 1976 proposed the first comprehensive statistical model relating mortality and cause-specific mortality. Preston used life tables from 43 national populations, including both developed countries such as United States and England and developing countries such as Chile, Colombia, Costa Rica, Guatemala, México, Panama, Taiwan, Trinidad and Tobago, and Venezuela. He used multiple linear regression to analyze the cause-specific-age-standardized death rates by sex. The estimated slopes represented the proportional contribution of each cause to a unit change in the total mortality rate. With the exception of neoplasms in both sexes and cardiovascular disease in males, all of the estimated slopes were positive and statistically significant. This demonstrated that the mortality rates from each specific cause were expected to decline as total mortality declined. The major causes accounting for the decline were all infectious and parasitic diseases.