At this time, the contemporary world is being divided in two by demographic forces: nearly half the world, including the industrial countries and China, is establishing a balance between births and deaths, leading to an improvement in living conditions; but in the other half, where birthrates remain high, rapid population growth is beginning to overwhelm local life support systems in many countries, leading to ecological deterioration and declining living standards. Existing demographic analysis fail to explain the negative relationships between population growth and life-support systems that now are emerging in scores of 3rd world countries. As the 1990s approach, new demographic criteria are needed. Countries now in their 4th decade of rapid population growth have failed to complete the demographic transition, and the drop in living standards is making it difficult for them to complete the demographic transition. Unless the relationship between rapidly multiplying populations and their life support systems can be stabilized, development policies are likely to fail. The remainder of this monograph directs attention to the following: carrying capacity stresses; diverging food and income trends; growing rural landlessness; population growth and conflict; the demographic trap of rapid population growth and the associated ecological and economic deterioration, which prevents completion of the demographic transition; national fertility declines; and completing the demographic transition. At this time, much of the world is making slow progress toward realizing the balance of birth and death rates needed to complete the demographic transition. Responsibility for stopping population growth remains both in the high growth regions that have the highest stake in averting the consequences of continued population growth, and in the low growth regions that can provide the financial and technical assistance necessary for successful family planning programs.