A study done in Thailand in a broader context of rapid fertility decline in a third-world setting reveals the use of four proximate determinants borrowed from the proximate determinant framework. Among other determinants, primary sterility and coital frequency have not been observed to influence the ongoing fertility decline (Knodel, 1979, Knodel, Chamrethirang and Debavalya, 1982). The conclusion arrived at by this study clearly mentions that, "Thailand's reproductive revolution is largely the product of increasing deliberate marital fertility control. In brief, Thailand has already entered into the most advanced stage of fertility transition." (