World Population Estimated at 8 Billion
Global Population Estimates Vary but Trends Are Clear: Population Growth Is Slowing
Using data from the International Database, the U.S. Census Bureau estimates the world population hit 8 billion on September 26.
Emphasis on the word estimates.
There are many sources of uncertainty in estimating the global population, and it’s unlikely this population milestone was reached on that exact date.
For example, the United Nations (U.N.) Population Division estimates the world population reached 8 billion on November 15, 2022.
Only around 4% of the world population (all in Africa) lives in a country with very high fertility — above 5 children per woman. Even in countries with very high fertility, fertility is generally lower than it was in the past.
Why the discrepancy? Many of the world’s most populous countries (such as India and Nigeria), haven’t conducted a census in over 10 years, and many countries lack civil registration and vital statistics systems that accurately record births and deaths among their population.
Given the lack of precise population data worldwide, the U.N. and Census Bureau estimates are not that far apart, and both imply similar overall trends.
Population Growing at Slower Pace
The rate of growth peaked decades ago in the 1960s and has been declining since and is projected to continue declining.
While it took 12.5 years for the world to go from 7 billion to 8 billion people, we project it will likely take 14.1 years to go from 8 billion to 9 billion, and another 16.4 years to go from 9 billion to 10 billion.
Despite a slowdown, we project the world population will reach 10.2 billion by 2060.
These broad global trends mask wide diversity. Population growth is the result of fertility, mortality, migration and the share of the population at certain ages. These trends all differ from country to country and, as a result, population growth varies around the world.
Declining Fertility Continues
Nearly three quarters (74%) of the earth’s population reside in countries where fertility is around or below the replacement level.
It is widely believed that 2.1 is the replacement-level fertility rate — the number of births a woman would need to have in her lifetime to replace herself and the father. However, the precise level of fertility necessary for long-term replacement varies between countries due to different mortality rates.
Around 33% of the world population — approximately 1 in 3 people — lives in a country with a fertility rate close to replacement, including diverse countries such as India, Tunisia and Argentina.
Demographers once assumed fertility would stop declining once it reached replacement levels. But it has continued to decline below replacement levels in many countries.
Around 15% of the world’s population lives in a country with low fertility of 1.6 to 1.8 children per woman. This includes a diverse range of countries like Brazil, Mexico, the United States and Sweden.
Another 26% — about 1 in 4 people — lives in a country with very low fertility at 1.5 children or fewer per woman. Such countries include China, South Korea and Spain.
Another 23% lives in a country with moderately high fertility between 2.3 and 5.0 children. This broad category includes a diverse range of countries like Papua New Guinea, Israel and Ethiopia.
Only around 4% of the world population (all in Africa) lives in a country with very high fertility — above 5 children per woman. Even in countries with very high fertility, fertility is generally lower than it was in the past.
And we project that by 2060, no country will have an average of four or more children per woman, let alone five or six children per woman.
It’s projected that Benin will have the world’s highest projected total fertility rate (3.8) in 2060. There will, of course, still be women who have four or more children, but it is unlikely entire countries will average four or more children per woman.
Most Growth Will Come From Adult Populations
The world population is projected to keep growing despite declining fertility rates. In fact, we estimate the number of infants already peaked in 2017. Instead, population growth in the future will come from larger groups of people at adult ages. Demographers call this phenomenon population momentum.
Figure 3 shows the world population by age in 2023 and the projected population by age in 2060. Population growth between now and 2060 will be from the population pyramid “filling up” previously sparse older age groups, not from growing numbers of births.
Figure 4 shows how the growth of the older-adult population is projected to make up most of the population growth between now and 2060. Future population growth will be coincident with population aging.
Global Aging
As fertility declines, there are proportionally fewer younger people and more older people.
The share of the population at young ages has been declining. Today, 32% of people are 19 or younger. By 2060, that number is projected to slip to 26%.
As the share of young people declines, the proportion of people at older ages increases. Today, 10% of the world is 65 or older and their share is projected to double to 20% by 2060.
As a result, the median age is changing. Today, the global median age is 32 (half the population is younger and half older). By 2060, however, the global median age is projected to climb to 39 years.
These general trends vary by country. Niger is the world’s youngest country, with a median age of 15 in 2023. Monaco, by contrast, is the oldest, with a median age of 56 in 2023.
Increasing Life Expectancy
In many countries where young-age mortality is already low, gains in life expectancy come from improving conditions at older ages.
Canada, for instance, did not experience big declines in young-age mortality between 2000 and 2023, but its total life expectancy increased by an average of about 4 years, largely from reduced mortality at older ages.
For many other countries, however, life expectancy trends are driven more by dramatic declines in child mortality. In Niger, for example, child mortality declined from around 224 deaths of children under 5 per 1,000 births in 2000 to 103 deaths per 1,000 births in 2023.
As a result, the country’s average life expectancy at birth increased from 45 years in 2000 to 60 years in 2023. We project that Niger will continue this trend and that child mortality will drop to 45 deaths per 1,000 births by 2060.
Life expectancy gains from reducing mortality at young ages make populations younger. As fewer children die, there are more children in the population.
While life expectancy is generally increasing, there are some exceptions. Many countries saw a decline in life expectancy due to the COVID-19 pandemic. We are gradually incorporating COVID-19 mortality into the population estimates available in the International Database (IDB) as more recent mortality data become available.
https://www.census.gov/library/stories/2023/11/world-population-estimated-eight-billion.html
世界人口估計為80億
全球人口估計值各不相同,但趨勢很明確:人口
增長正在放緩
美國人口普查局 使用國際資料庫的數據估計,9月26日世界人口達到80億。
強調單詞估計。
估計全球人口的不確定性來源有很多,而且這個人口里程碑不太可能在那個確切的日期達到。
例如,聯合國人口部估計,2022 年 11 月 15 日世界人口達到 80 億。
世界上只有大約 4% 的人口(全部在非洲)生活在一個生育率非常高的國家——每名婦女生育 5 個孩子以上。即使在生育率非常高的國家,生育率通常也比過去低。
為什麼會有這種差異?世界上許多人口最多的國家(如印度和奈及利亞)已經 10 多年沒有進行過人口普查,許多國家/地區缺乏準確記錄其人口出生和死亡的民事登記和生命統計系統。 鑒於全球缺乏精確的人口數據,聯合國和人口普查局的估計值相差不遠,都意味著相似的總體趨勢。
人口增長速度較慢
增長率在幾十年前的 1960 年代達到頂峰,此後一直在下降,預計還會繼續下降。 雖然世界人口從 70 億增加到 80 億人口需要 12.5 年時間,但我們預計從 80 億人口增加到 90 億人口可能需要 14.1 年,再花 16.4 年時間才能從 90 億人口增加到 100 億人口。
儘管經濟放緩,但我們預計到 2060 年,世界人口將達到 102 億。
這些廣泛的全球趨勢掩蓋了廣泛的多樣性。人口增長是生育率、死亡率、移民和特定年齡人口份額的結果。這些趨勢都因國家而異,因此,世界各地的人口增長各不相同。
生育率持續下降
地球上近四分之三 (74%) 的人口生活在生育率接近或低於更替水平的國家。 人們普遍認為,2.1 是更替水準的生育率——女性一生中需要生育的生育次數才能取代自己和父親。然而,由於死亡率不同,長期替代所需的確切生育水準因國家而異。 世界上大約 33% 的人口(約每 3 人中就有 1 人)生活在生育率接近更替的國家,包括印度、突尼西亞和阿根廷等不同國家。
人口統計學家曾經認為,一旦生育率達到更替水準,生育率就會停止下降。但在許多國家,生育率繼續下降到低於更替水準.
世界上大約 15% 的人口生活在一個生育率低的國家,每名婦女生育 1.6 至 1.8 個孩子。這包括巴西、墨西哥、美國和瑞典等多個國家。
另有26%(約四分之一的人)生活在生育率非常低的國家,每名婦女生育1.5個孩子或更少。這些國家包括中國、韓國和西班牙.
另有23%的人生活在2.3至5.0名兒童的中等高生育率國家。這個廣泛的類別包括巴布亞紐幾內亞、以色列和衣索比亞等多個國家。
世界上只有大約 4% 的人口(全部在非洲)生活在一個生育率非常高的國家——每名婦女生育 5 個孩子以上。即使在生育率非常高的國家,生育率通常也比過去低。
我們預計,到2060年,沒有一個國家平均每名婦女生育4個或更多孩子,更不用說每個婦女生育5到6個孩子了。
預計到 2060 年,貝寧的預計總生育率 (3.8) 將是世界上最高的。當然,仍然會有婦女生育四個或更多孩子,但整個國家不太可能平均每個婦女生育四個或更多孩子。
大多數增長將來自成年人群
儘管生育率下降,但預計世界人口仍將保持增長。事實上,我們估計嬰兒數量在 2017 年已經達到峰值。相反,未來的人口增長將來自更大的成年群體。
人口統計學家將這種現象稱為人口動量。 圖 3 顯示了 2023 年按年齡劃分的世界人口,以及 2060 年按年齡劃分的預測人口。從現在到 2060 年的人口增長將來自人口金字塔「填滿」以前稀疏的老年群體,而不是來自不斷增長的出生人數。
圖 4 顯示了從現在到 2060 年,老年人口的增長預計將如何佔人口增長的大部分。未來的人口增長將與人口老齡化同步。
全球老齡化
隨著生育率的下降,年輕人的比例會減少,老年人會成比例地增加。
年輕人口的比例一直在下降。今天,32% 的人年齡在 19 歲或以下。到 2060 年,這一數字預計將下滑至 26%。
隨著年輕人比例的下降,老年人口的比例增加。今天,世界上 10% 的人口年齡在 65 歲或以上,預計到 2060 年,他們的份額將會雙倍,達到 20%。
因此,年齡中位數正在發生變化。今天,全球人口的中位年齡為32歲(一半人口年輕,一半老年人)。然而,到 2060 年,全球中位年齡預計將攀升至 39 歲。 這些總體趨勢因國家/地區而異。尼日是世界上最年輕的國家,2023 年的中位年齡為15歲。相比之下,摩納哥年齡最大,2023 年的中位年齡為56歲。
延長預期壽命
在許多年輕死亡率已經很低的國家,預期壽命的增加來自老年條件的改善。 例如,加拿大在 2000 年至 2023 年期間的年輕死亡率並沒有大幅下降,但其總預期壽命平均增加了約 4 年,這主要是由於老年人死亡率的降低。
然而,對於許多其他國家來說,預期壽命趨勢更多地是由兒童死亡率的急劇下降驅動的。例如,在尼日爾,兒童死亡率從 2000 年的每 1000 名新生兒中約 224 名 5 歲以下兒童死亡下降到 2023 年的每 1000 名新生兒中約 103 人死亡。
因此,該國的平均出生預期壽命從2000年的45歲增加到2023年的60歲。我們預計,尼日爾將繼續這一趨勢,到 2060 年,兒童死亡率將降至每 1,000 名新生兒中有 45 人死亡。
通過降低年輕死亡率而增加的預期壽命使人口更年輕。隨著兒童死亡的減少,人口中的兒童也就越多。
雖然預期壽命普遍在增加,但也有一些例外。由於 COVID-19 大流行,許多國家的預期壽命下降。隨著更新的死亡率數據的獲得,我們正在逐步將 COVID-19 死亡率納入國際資料庫 (IDB) 中可用的人口估計中。