「Global Demography: Tectonic Shifts」と題したConversable EconomistブログエントリでTim Taylorが、人口動態を特集したIMFの季刊誌「Finance & Development」*13月号から、デビッド・ブルーム(David Bloom)ハーバード大教授の筆頭論文「Taking the Power Back」の内容を引用している。以下はその孫引き。


Ninety-nine percent of projected [population] growth over the next four decades will occur in countries that are classified as less developed—Africa, Asia (excluding Japan), Latin America and the Caribbean, Melanesia, Micronesia, and Polynesia. Africa is currently home to one-sixth of the world’s population, but between now and 2050, it will account for 54 percent of global population growth. Africa’s population is projected to catch up to that of the more-developed regions (Australia, Europe, Japan, New Zealand, and northern America—mainly Canada and the United States) by 2018; by 2050, it will be nearly double their size. ...
Between now and mid-2050, other notable projected shifts in population include:

  • India surpassing China in 2022 to have the largest national population;
  • Nigeria reaching nearly 400 million people, more than double its current level, moving it ahead of Brazil, Indonesia, Pakistan, and the United States to become the world’s third-largest population;
  • Russia’s population declining 10 percent and Mexico’s growing slightly below the 32 percent world rate to drop both countries from the top 10 list of national populations, while the Democratic Republic of the Congo (153 percent increase) and Ethiopia (90 percent) join the top 10; and
  • Eighteen countries—mostly in eastern Europe (and including Russia)—experiencing population declines of 10 percent or more, while 30 countries (mostly in sub-Saharan Africa) at least double their populations.


  • インドは2022年に中国を追い越し、世界最大の人口を持つ国になる。
  • ナイジェリアは現在の倍以上の4億人近くに達し、ブラジル、インドネシアパキスタン、米国を上回る世界第三の人口大国になる。
  • ロシアの人口は10%低下し、メキシコの伸びは世界平均の32%を僅かに下回る。その結果、両国とも人口の十大大国の座から滑り落ち、代わってコンゴ民主共和国(153%増)とエチオピア(90%増)がトップテン入りする。
  • 18ヶ国(大半がロシアおよび東欧諸国)が10%ないしそれ以上の人口減少を経験する半面、30ヶ国(大半がサハラ以南のアフリカ)で人口が倍以上になる。

More than half the world’s population now lives in urban areas, up from 30 percent in 1950, and the proportion is projected to reach two-thirds by 2050 . ... The number of megacities—urban areas with populations greater than 10 million—grew from 4 in 1975 to 29 today. Megacities are home to 471 million people—12 percent of the world’s urban population and 6 percent of the world’s total population. The United Nations recently introduced the concept of metacities, which are urban areas with 20 million or more residents. Eight cities had reached “meta” status in 2015. Tokyo heads the list, with 38 million residents—more than the population of Canada. No. 2 Delhi’s 26 million exceeds Australia’s population. Other metacities are Shanghai, São Paulo, Mumbai, Mexico City, Beijing, and Osaka. By 2025, Dhaka, Karachi, Lagos, and Cairo are projected to grow into metacities.


Japan’s median age of 47 is the world’s highest and is projected to rise to 53 by 2050. But by then South Korea’s median age will be 54. In 2050, 34 countries will have median ages at or above Japan’s current 47. The world’s 15- to 24-year-olds now outnumber those ages 60 and above by 32 percent. But by 2026 these two groups will be equal in size. After that, those over age 60 will rapidly come to outnumber adolescents and young adults. This crossover already took place in 1984 among advanced economies and is projected to occur in 2035 in less-developed regions.

*1:「the Big Squeeze/Global Population Pressures」という特集タイトルをあしらった表紙には、山手線で駅員が乗客を電車に押し込む写真が使われている。