I'm Jonathan Tomkin from the University of Illinois. In the previous lecture we discussed how much of the world had experienced a demographic transition. That is, death rates declined and so populations increased. But then birth rates came down as well and so now many countries in the world have birth and death rates that are now at a new lower level, and are not experiencing much population growth. Much of our worries about sustainability are connected to population growth. Are we gonna have J-shape growth curve that is exponential leading to an inevitable crash? Or will we have more of a soft landing if you like, with a S-shape curve were we grow to meet some kind of carrying capacity? So in this lecture we are going to examine some of the forces that might be behind determining which trajectory the world's population will follow. Here we have a diagram of a large group of people, in a big country. This is one of the things that's going on in the world today; is that we're seeing a huge increase in urbanization. So although some countries like China have very large populations, what we're going to learn is that this doesn't mean that they have very high rates of growth. What's more, it's possible to predict the rates of growth given both historical trends and the status of the populations that we have today. These tools aren't perfect but they give us a very good sense of some general trends for the next few decades. Here's a diagram which shows two photos. We have a young lady from Yemen, and older woman from Greece. It turns out that the median age -- that is, the person who is in the middle of the age distribution -- for Yemen is 18 years old. Half of Yemen's population is 18 or younger. In contrast, Greece's population has a median age of 42.5. So, just knowing this one fact, we can already think about "What do we predict in terms of population growth for these different countries?" Which group do you think is going to experience the most population growth in the next few decades? I'm sure you picked Yemen. And this is actually something that demographers do when they look forward to the world population and try to predict how it will change. Younger populations do imply higher fertility rates. Old people don't have kids in the same way that young people do. This is the map of the world that shows average ages of different countries. Lighter colors mean younger ages, while the countries in places like Europe, Canada and Japan indicate average ages in the 40s. Just like we saw Greece had an average age of 42.5. I'm 38, which means I'm actually the average age for the United States or for Australia. You can use this map to try and figure out if you're above, below, or at the average age in your country. Using this map, would you predict fertility rates to be higher or lower in different countries? I guess you would. Which country do you think fertility rates is the highest in? You might have said countries in sub-Saharan Africa, Yemen, Sri Lanka or Afghanistan. Notice how the median age of people in this, in these countries, is in their teens. Very young populations, with these averages below 20 years old, have lots of potential for population growth because there’s lots of people who have a long, fertile history ahead of them. Here on this map we see the world fertility rates for different countries and the hot colors -- the purples, the pinks, the reds -- indicate populations in which fertility is 4, 5, 6, or 7 births per woman. The darker colors -- the dark blues -- indicate places there are 2 or less births per woman. And from this you can see the places that have very young populations also have very high fertility rates. And so we can see immediately there’s a connection between the current demography -- that is, the current population age structure -- and future expected population growth. Note also that the older countries have much lower fertility, those blue countries in this map. In many places the birth rate is below 2.1. 2.1 is considered to be the population break-even point, if you like. That’s the place where we have enough births per woman, 2.1 births per woman, to make up for, the deaths that occur in a population. It’s not exactly 2 because there is a slight imbalance between the number of women and men born and, we have to worry about things like deaths in childhood and so on. So, many countries are below 2.1, which indicates that they’re on track for either population staying the same or declining in the future. And in fact we do see population growth rates that are negative in some countries. This is a map of growth rates. Note how Eastern Europe, Russia and Japan a negative growth rates in other words, their populations are declining Young, high birth rate countries have high growth rates So, this make some countries ... Southafrica, Afganistan, Yemen or same places are seeing fast population growth. It's very unequal around the world because different countries different stages of the demographic transition So what determines these high birth rates, and can they be changed? A lot of people spend a lot of effort trying to figure out policies to change birth rates in some countries in the world today in advanced economies ... increase birth rates Australia have a babybonus earn money having children other countries like Singapore have lots of programs to increase their birth rates On the other hand, other countries are looking at decreasing their birth rates. China is the most well known example of that. Are there other factors apart from these policy prescriptions that might do something to change birthrates? One very clear relationship is that as countries become wealthier their birth rates decrease. Here's a map of the total fertility rate - children per woman - vs GDP per person. That's a measure of individual wealth. As we can see the world average is a little bit above replacement rate. but there's a very strong correlation as the GDP per capita increases the fertility rate is much lower There appears to be a point ...countries per count ....income country where the GDP is sufficiently high that birth rates are at or below the replacement rate ...countries...Notice also if you look at the very poor countries they are the countries with very high fertility factors. As can we see... in this graph the low GDP per person countries are poor countries ...factors You might be able to see where the United States - one of the world's richest countries - also has a relatively low fertility factor. But there are inconsistencies in this graph. f.e. Saudi Arabia has a much higher fertility than other countries in the similar level of development, the countries similar level of GDP per person Similar countries, with similar GDPs have birth rates that are below two, whereas Saudi Arabia's are close to four, close to double that So, it might be that there are other cultural factors f.e. social status of women, that also contribute to the birth rates When women marry later, they have less children. US women marry on average when they are in their mid-twenties. And the US has a replacement fertility rate - about two births per woman. The top four countries shown here have much lower marriage ages as you can see in their mid teens. ...so much... can see the social expectation women can do Similarly education seem to be important correlation between increased education and decreased fertility In all countries shown here more education for women is associated with lower fertility. So to explain this graph: each of the countries listed has 3 bars. The light blue bar means the woman has no education. dark blue primary education As you can see for every one of these countries shown, from Kenya to Bangladesh, as the amount of education for women increases so does the fertility rate decrease. ... close to the replacement rate for highly educated women very high fertility rates in these countries. You should be careful interpreting data like this. There's not necessarily a causal relationship that's direct. It could be quite complicated. f.e. If you're in school, you're not having kids. If you're in school, you're probably more valuable as an employee... ...being educated rather than having children and a family, or in the workforce ... rather than having children So we have to be careful about policy prescriptions from this but we can see a clear trend. given that the world today has recently seen be increased level of wealth human rights and education Does this imply that we could expect that rates of population growth will decrease in the near future?... In the next lecture we'll make a prediction about what the world's population will be over the course of this century and I will tell you if I think we're heading for a J style Crash or a smooth S style soft landing Produce by OCE ATLAS digital media at the University of Illinois -Champain
