During the second stage, improvements in hygiene, medical care, and food pro-duction led to a decrease in the death rate in newly industrializing regions of WesternEurope. However, birth rates remained high due to tradition and because many peoplewere involved in agrarian occupations. The combination of a lowered CDR and a stableCBR led to dramatic increases in population starting at the beginning of the nineteenthcentury.<br> In stage three, birth rates also began to fall. In cities there was less incentive toproduce large numbers of children, since city dwellers no longer worked the land, andthe cost of raising children in an urban environment was greater than in rural districts.Furthermore, more children survived into adulthood due to improved living condi-tions. These economic pressures led to a lower CBR and over time the numbers of peo-ple being born started to approximate the numbers dying.<br> The final stage, which some demographers have called the postindustrial stage, oc-curs when birth rates and death rates are about equal. In this case there is zero naturalpopulation growth. Over time the birth rate may fall below the death rate, and withoutimmigration the total population may slowly decrease. By the early twenty-first centu-ry, several European countries were experiencing population declines due to the CDRoutstripping the CBR. For example, in Italy in 2004 there were about 9 births per thou-sand against 10 deaths per thousand.<br> The demographic transition took about 200 years to complete in Europe. Many de-veloping countries are still in stage two of the demographic transition model: births faroutstrip deaths. In these countries, CDR has declined due to improvements in sanita-tion and increases in food productivity, but the birth rate has still not adjusted down-ward to the new realities of improved living conditions. The imbalance of births overdeaths in the developing world is the fundamental reason for the dramatic populationexplosion in the latter half of the twentieth century. However, population statisticsindicate that in many less developed countries the CBRs have begun to decline overrecent decades, giving rise to optimism in some quarters about future trends. The rapidindustrialization of many parts of the developing world has meant that these countrieshave reached stage three of the model much faster than countries in the developedworld did during the nineteenth century. This fact has led many demographers to pre-dict that world population will reach an equilibrium level sooner and at a lower totalthan more pessimistic earlier predictions.
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