system of government in which all 'citizens' (however defined) have equal political and legal rights, privileges, and protections, as in the Greek city-state of Athens in the fifth and fourth centuries B.C.E. Demographic Transition,A change in the rates of population growth. Before the transition, both birth and death rates are high, resulting in a slowly growing population; then the death rate drops but the birth rate remains high, causing a population explosion. (867)