Utilizing a sample of 2964 unmarried women over the period 1979-88 from the US National Longitudinal Survey of Youth, a test was performed to determine the causal direction of relationship between receipt of aid to families with dependent children (AFDC) and the decision to have a non-marital birth. The existence of 'causality' is defined as the lack of a simultaneous relationship or joint dependency between these variables. One of the most interesting findings was a failure to reject the hypothesis that these choices are jointly determined. Both were found to depend upon variables that are demographic, economic, personal, and family-related. The profiles derived from the specification and estimation of a simultaneous equation system with discrete endogenous variables depict a woman whose fertility and economic decisions were predominantly based on economic deprivation, demographic situation and family instability.