Long-term population projections: Scenarios of low or rebounding fertility.
The size of the human population is projected to peak in the 21st century. But quantitative projections past 2100 are rare, and none quantify the possibility of a rebound from low fertility to replacement-level fertility. Moreover, the most recent long-term deterministic projections were published a...
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| Language: | English |
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Public Library of Science (PLoS)
2024-01-01
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| Series: | PLoS ONE |
| Online Access: | https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0298190&type=printable |
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| _version_ | 1846169230520614912 |
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| author | Dean Spears Sangita Vyas Gage Weston Michael Geruso |
| author_facet | Dean Spears Sangita Vyas Gage Weston Michael Geruso |
| author_sort | Dean Spears |
| collection | DOAJ |
| description | The size of the human population is projected to peak in the 21st century. But quantitative projections past 2100 are rare, and none quantify the possibility of a rebound from low fertility to replacement-level fertility. Moreover, the most recent long-term deterministic projections were published a decade ago; since then there has been further global fertility decline. Here we provide updated long-term cohort-component population projections and extend the set of scenarios in the literature to include scenarios in which future fertility (a) stays below replacement or (b) recovers and increases. We also characterize old-age dependency ratios. We show that any stable, long-run size of the world population would persistently depend on when an increase towards replacement fertility begins. Without such an increase, the 400-year span when more than 2 billion people were alive would be a brief spike in history. Indeed, four-fifths of all births-past, present, and future-would have already happened. |
| format | Article |
| id | doaj-art-e126e83cdcb249c6af1ad0cbf2642b82 |
| institution | Kabale University |
| issn | 1932-6203 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj-art-e126e83cdcb249c6af1ad0cbf2642b822024-11-13T05:31:40ZengPublic Library of Science (PLoS)PLoS ONE1932-62032024-01-01194e029819010.1371/journal.pone.0298190Long-term population projections: Scenarios of low or rebounding fertility.Dean SpearsSangita VyasGage WestonMichael GerusoThe size of the human population is projected to peak in the 21st century. But quantitative projections past 2100 are rare, and none quantify the possibility of a rebound from low fertility to replacement-level fertility. Moreover, the most recent long-term deterministic projections were published a decade ago; since then there has been further global fertility decline. Here we provide updated long-term cohort-component population projections and extend the set of scenarios in the literature to include scenarios in which future fertility (a) stays below replacement or (b) recovers and increases. We also characterize old-age dependency ratios. We show that any stable, long-run size of the world population would persistently depend on when an increase towards replacement fertility begins. Without such an increase, the 400-year span when more than 2 billion people were alive would be a brief spike in history. Indeed, four-fifths of all births-past, present, and future-would have already happened.https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0298190&type=printable |
| spellingShingle | Dean Spears Sangita Vyas Gage Weston Michael Geruso Long-term population projections: Scenarios of low or rebounding fertility. PLoS ONE |
| title | Long-term population projections: Scenarios of low or rebounding fertility. |
| title_full | Long-term population projections: Scenarios of low or rebounding fertility. |
| title_fullStr | Long-term population projections: Scenarios of low or rebounding fertility. |
| title_full_unstemmed | Long-term population projections: Scenarios of low or rebounding fertility. |
| title_short | Long-term population projections: Scenarios of low or rebounding fertility. |
| title_sort | long term population projections scenarios of low or rebounding fertility |
| url | https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0298190&type=printable |
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