16.8: Chapter 8
- Page ID
- 310039
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00:07 Russia, with the largest territory in the world,
00:10 has roughly the same total population as Nigeria,
00:13 a country 1/16 its size.
00:16 But this similarity won't last long.
00:18 One of the populations is rapidly growing,
00:21 while the other is slowly declining.
00:23 What can this tell us about the two countries?
00:25 Population statistics are some of the most important data
00:29 social scientists and policy experts have to work with.
00:33 But understanding a country's situation
00:35 and making accurate predictions
00:37 requires knowing not just the total size of the population
00:40 but its internal characteristics,
00:42 such as age and gender distribution.
00:45 So, how can we keep track of all that data
00:47 in a way that makes it easy to comprehend?
00:49 Complex data is more easily interpreted
00:51 through visualization,
00:53 and one of the ways that demographers represent
00:55 the internal distribution of a population
00:57 is the population pyramid.
01:00 Here, the data is divided by gender
01:02 with females on one side and males on the other.
01:05 The population numbers are shown
01:07 for each five-year age interval,
01:09 starting from 0-4
01:10 and continuing up to 100 and up.
01:12 These intervals are grouped together
01:14 into pre-reproductive (0-14),
01:17 reproductive (15-44),
01:20 and post-reproductive years (45 and up).
01:23 Such a population pyramid can be a powerful predictor
01:26 of future population trends.
01:28 For example,
01:29 Rwanda's population pyramid shows it to be a fast-growing country,
01:33 with most of the population
01:34 being in the youngest age groups at the bottom of the pyramid.
01:37 The number will grow rapidly in the coming years.
01:39 As today's children reach their reproductive years
01:42 and have children of their own,
01:44 the total population is almost certain to double
01:47 within the next few decades.
01:48 For our second example,
01:50 let's look at Canada,
01:51 where most of the population is clustered
01:53 around the middle of the graph.
01:55 Because there are less people
01:56 in the pre-reproductive age groups
01:58 than there are in the reproductive ones,
02:00 the population will grow more slowly,
02:03 as the number of people reaching their reproductive years decreases.
02:06 Finally, let's look at Japan.
02:09 Because the majority of its population
02:11 is in its post-reproductive years
02:13 and the number of people is smaller
02:15 at each younger interval,
02:16 this means that at current rates of reproduction
02:18 the population will begin to decline
02:20 as fewer and fewer people reach reproductive age.
02:24 Comparing these three population pyramids
02:26 side by side
02:27 shows us three different stages
02:29 in a demographic transition,
02:30 as a country moves from a pre-industrial society
02:33 to one with an industrial
02:34 or post-industrial economy.
02:36 Countries that have only recently begun
02:38 the process of industrialization
02:40 typically see an increase in life expectancy
02:42 and a fall in child mortality rates
02:45 as a result of improvements
02:46 in medicine, sanitation, and food supply.
02:49 While birth rates remain constant,
02:51 leading to a population boom.
02:53 Developing countries that are farther along
02:55 in the industrialization process
02:57 begin to see a fall in birth rates,
02:59 due to factors such as
03:00 increased education and opportunities for women outside of child-rearing
03:04 and a move from rural to urban living
03:07 that makes having large families
03:09 less economically advantageous.
03:11 Finally, countries in advanced stages of industrialization
03:14 reach a point
03:15 where both birth and death rates are low,
03:18 and the population remains stable
03:20 or even begins to decline.
03:21 Now, let's take a look at the projected population pyramids
03:24 for the same three countries in 2050.
03:27 What do these tell us
03:29 about the expected changes
03:30 in each country's population,
03:32 and what kinds of factors
03:33 can alter the shape of these future pyramids?
03:36 A population pyramid can be useful
03:38 not only as a predictor of a country's future
03:40 but as a record of its past.
03:42 Russia's population pyramid
03:44 still bears the scars of World War II,
03:47 which explains both the fewer numbers of elderly men
03:50 compared to elderly women
03:52 and the relatively sudden population increase
03:54 as soldiers returned from the war
03:56 and normal life resumed.
03:58 China's population pyramid
03:59 reflects the establishment of the one child policy
04:02 35 years before,
04:04 which prevented a population boom
04:06 such as that of Rwanda
04:07 but also led to sex-selective abortions,
04:10 resulting in more male children than female children.
04:13 Finally, the pyramid for the United States
04:16 shows the baby boom that followed World War II.
04:19 As you can see,
04:20 population pyramids tell us far more
04:22 about a country
04:23 than just a set of numbers,
04:25 by showing both where it's been
04:26 and where it's headed
04:28 within a single image.
04:29 And in today's increasingly interconnected world,
04:31 facing issues such as food shortages,
04:33 ecological threats, and economic disparities,
04:36 it is increasingly important
04:38 for both scientists and policy makers
04:40 to have a rich and complex understanding
04:43 of populations and the factors affecting them
“Population Pyramids: Powerful Predictors of the Future” by Kim Preshoff is licensed by TED under CC BY-NC-ND 4.0