Statistical correlations between demographic events in a 75-year study

Population is an extremely dynamic element of the whole socio-economic sphere. Its natural movement includes processes related not only to births and deaths, but also to marriages, divorces, and abortions. In Romania the natural increase became negative in 1992 (-0.2/1000 inhabitants), reached a minimum in 2002 (-2.7/1000 inhabitants) and is still continuing to be negative. Using the “Romania Statistical Annuals”, we collected information referring to these demographic events for 75 years (1930-2004). We selected the data of 31 years when important regulations regarding the family functions were taken by the government (it is especially about abortion legislation). We found numerous statistically significant correlations between these events, which suggest their interdependence. We consider the rate of births as a dependent variable, respectively the rate of marriages and the rate of divorces as independent variables. Using the linear regression analysis (SPSS Program), we obtained the equation "rate of births = 4.714 + 3.049 x rate of marriages – 9.061 x rate of divorces". That means the rate of divorces has a negative influence on the rate of births, and this influence is three times stronger than the influence of the rate of marriages (which is a positive one). The model we obtained was validated through other statistical tests – ANOVA test and the bootstrap method.