At the beginning of the Demographic Transition (DT) the Crude Birth Rates (CBR) and Crude Death Rates (CDR) are generally high 35-40 per 1000. At the end of the transition process (i.e., Stage 4) the rates are very low, approximately 10 per 1000 but the total population of the country is much higher in Stage 4 than in Stage 1. Fully explain why?