Chapter 7 - Population, page 1 of 9• two questions underlie this chapter:1. is population growth a threat to economic development?2. what should be done about population growth?• population growth and development:• the Solow growth model suggests faster population growth leads to a lower per capitaincome• however, the effect of population growth on development is uncertain; although mosteconomists believe population growth is bad for development, the empirical evidence isunclear• economic development leads to lower population growth; however, it is unclear iflower population growth leads to greater development• developing countries could offer family planning as a health measure, which couldreduce population growth• the history of human population can be divided into 4 epochs:1. the pre-agricultural era (until about 10,000 years ago):• in this era, the population was limited by the hunting, gathering, and fishingcarrying capacity of the environment; the invention of agriculture allowed the landto support a greater number of people• it is estimated that there were between 10 million to 100 million humans living atthe end of the pre-agricultural era• it is estimated that there were at least 60,000 years or as much as 3 million years ofhuman history in the pre-agricultural era, depending on where one draws the linebetween anatomically modern humans and similar ancestors• population densities were low during this era2. from the invention of agriculture to the beginning of the Industrial Revolution(around 1800):• agriculture developed at different rates in different parts of the world• as agriculture spread, population densities increased• by the beginning of the Industrial Revolution, the human population hadincreased to 1.7 billion (about 17 times greater than it was 10,000 years before)3. the Industrial Revolution to World War II (1945):• the world population growth rate during this period was higher than it was duringthe first two eras• by 1945 the world population was about 2.5 billion4. post-World War II:• the world population doubled to about 5 billion by 1990 and increased to about 6billion in 2000• by some estimates, most people who have lived are alive today• will the world population continue to grow rapidly?• if the world population continues to grow rapidly, in 100 years the world populationwould be about 30 billion• however, various factors will probably eventually stop the human population fromgrowing further; according to Malthus, when income per person is greater than thesubsistence level, the population grows because families that have an income levelgreater than the subsistence level will have more children; the additional childrenreduce income per person back to the subsistence levelChapter 7 - Population, page 2 of 9• however, population growth slows without Malthusian checks; empirically, theopposite of what Malthus expected is observed – groups with higher incomes havelower fertility rates• the demographic transition:• the crude birth rate is defined as the number of births per thousand people• the crude death rate is defined as the number of deaths per thousand people• the rate of natural increase is defined as the crude birth rate minus the crude deathrate; the rate of natural increase is usually adjusted to percent terms (that is, it isadjusted to per hundred people); for example, if the birth rate is 38 per thousand and thedeath rate is 28 per thousand, then the rate of natural increase is (38-28)/1000 = 10/1000= 1/100 = 1%; the rate of natural increase is the rate at which the population grows,excluding immigration and emigration• as a society become richer, the death rate declines; the decline in the death tends toprecede that in the birth rate• page 250, figure 7-1 – the birth and death rates in England and Wales from 1750 to1950rates perthousandbirth ratedeath rate1750 1950• the vertical distance between the birth rate and the death rate is the rate ofnatural increase; the smaller the gap between the birth rate and the death rate,the lower the population growth rate• as a country develops, the population growth rate increases; with furtherdevelopment, the population growth rate decreases as the birth rate approachesthe death rate; this trend is illustrated in the figure above by the gap between thebirth rate and death rate• page 251, figure 7-2 – illustrates the birth and death rates in Ceylon (Sri Lanka) from1905-1995:Chapter 7 - Population, page 3 of 9rates perthousandbirth ratedeath rate1905 1995• the death rate drops because of improved healthcare technology (immunizations,antibiotics, etc.) and better sanitation• why does the birth rate decline after the decline in the death rate?• perhaps families have an ideal family size in mind; when death rates are high,they will have more children to meet this target; for example, if the infantmortality rate is 1/3, then parents might have 3 or more children to ensure that atleast one survives into adulthood to take care of the parents in old age; however,if children have a 95% chance of survival into adulthood, then the parents mighthave only one child• as larger families become less necessary, cultural norms could still encouragepeople to have many children; cultural norms that encourage large families couldchange slowly over time• the rate of natural increase in a country increases as the gap between the birth rate andthe death rate grows; this could be why the population growth rate in some developingcountries is so high; extrapolating to where the birth rate is about equal to the death ratesuggests that the population size will stabilize close to the replacement rate• there is cross-country evidence that suggests the population growth rate in a countrywill eventually stabilize; for instance, some European countries have a fertility ratebelow the replacement level• there is a negative correlation between the level of income and the population growthrate in intercountry and intracountry data: the population growth rate is highest in thepoorest countries; in countries with high inequality, the poorest households and thepoorest regions have the highest fertility• population growth decline because of greater average income per capita (and possiblybecause of higher levels of education)• a change in the structure of the economy contributes to the decline in the birth ratebecause people are employed for wages instead of