Every forecast, kept — and scored as the years arrive
The forecasts disagree about 2100 by 2.1B people
World population: the 2024 revision (estimates solid, current projection dashed) with each earlier revision's forward projection from its vintage.
| Revision | 2050 | 2100 |
|---|---|---|
| UN 2010 | 9.31B | — |
| UN 2012 | 9.55B | 10.85B |
| WIC 2013 | 9.14B | 8.95B |
| UN 2015 | 9.73B | — |
| UN 2017 | 9.77B | — |
| WIC 2018 | 9.38B | 9.28B |
| UN 2019 | 9.74B | 10.88B |
| IHME 2020 | 9.55B | 8.79B |
| UN 2022 | 9.71B | 10.35B |
| WIC 2023 | 9.59B | 9.89B |
| Census 2025 | — | — |
| UN 2024 (current) | 9.66B | 10.18B |
un-wpp (archival revisions) · release 2026.08.5
World population, 2024 revision and each earlier revision's projection
4 series: UN 2024 (2000–2100, latest 10.18B, projected); IHME 2020 (2017–2100, latest 8.79B, projected); UN 2022 (2021–2100, latest 10.35B, projected); WIC 2023 (2020–2100, latest 9.89B, projected).
How far off were they?
Bias, by revision and horizon
World population. Positive mean bias: the revision’s projected population came in above what materialized (over-projected). Negative: under-projected.
| Revision | Horizon (years) | Mean bias | MAPE | Over-projected |
|---|---|---|---|---|
| UN 2010 | 1-5 | -2407313.235 | 5.7% | — |
| UN 2010 | 6-10 | -3242627.033 | 7.6% | — |
| UN 2010 | 11-15 | -3351580.923 | 8.7% | — |
| UN 2012 | 1-5 | -1914412.422 | 5.0% | — |
| UN 2012 | 6-10 | -2439776.845 | 6.6% | — |
| UN 2012 | 11-15 | -2317931.845 | 7.6% | — |
| UN 2015 | 1-5 | -1927986.895 | 5.5% | — |
| UN 2015 | 6-10 | -1603022.010 | 6.5% | — |
| UN 2017 | 1-5 | -1396718.111 | 4.5% | — |
| UN 2017 | 6-10 | -1012183.073 | 5.7% | — |
| UN 2019 | 1-5 | -1101102.033 | 4.4% | — |
| UN 2022 | 1-5 | -686256.764 | 2.6% | — |
| IHME 2020 | 1-5 | -190591.879 | 5.7% | — |
| WIC 2013 | 1-5 | -3451975.065 | 6.3% | — |
| WIC 2018 | 1-5 | -1733629.115 | 4.6% | — |
| IHME 2020 | 6-10 | +83257.579 | 6.4% | — |
| WIC 2013 | 6-10 | -4302266.043 | 8.1% | — |
release 2026.08.5
Country probe
Pick a country to compare its actual total fertility rate against what each revision projected.
Total fertility rate: actual vs. revisions
Select a country above to see its projection history.
Methodology
How scores are computed
Every projection score compares one revision’s projected value, at a given future year, to the value the scoring release’s current data now reports for that same year and entity.
- error
- projected − actual
- relError
- error / actual
- horizon
- year − estimateEndYear
Mean bias is the average of error across scored rows; MAPE is the average of |relError|. Rows are bucketed by horizon into 1-5, 6-10, and 11-15 years out; horizons beyond 15 years are not scored.
Actuals are the scoring release's current best estimates and are themselves revisable.
Forecasters
Wittgenstein Centre (WIC) — SSP2 (Medium) scenario
The Wittgenstein Centre for Demography and Global Human Capital (IIASA) publishes population and total-fertility-rate projections disaggregated by education level, aggregated here to national and world totals; three vintages are scored on the accuracy page (2013, 2018, 2023).
License: Custom (IIASA/WIC, unconfirmed). Wittgenstein Centre for Demography and Global Human Capital (WIC), Wittgenstein Centre Data Explorer Version 1.0, 2013. Wittgenstein Centre for Demography and Global Human Capital (WIC), Wittgenstein Centre Data Explorer Version 2.0, 2018. Wittgenstein Centre for Demography and Global Human Capital (WIC), Wittgenstein Centre Data Explorer Version 3.0 (Beta), 2023.
Not available through this platform’s public API under this source’s license; shown on this page with attribution only.
IHME — reference scenario
The Institute for Health Metrics and Evaluation (IHME) publishes a reference-scenario population and fertility forecast for 195 countries and territories through 2100 (Vollset et al., The Lancet, 2020); one vintage (2020) is scored on the accuracy page.
License: IHME Free-of-Charge Non-Commercial User Agreement. Vollset SE, et al. Fertility, mortality, migration, and population scenarios for 195 countries and territories from 2017 to 2100: a forecasting analysis for the Global Burden of Disease Study. The Lancet. 2020.
Not available through this platform’s public API under this source’s license; shown on this page with attribution only.
U.S. Census Bureau (IDB) — central (single, no named alternatives) scenario
The U.S. Census Bureau's International Database (IDB) publishes a single central population projection per country, with no named alternative scenarios; one vintage (2025) is scored on the accuracy page.
License: Public domain (17 U.S.C. §105). U.S. Census Bureau, International Database.
Every forecaster above is scored against the same actuals (the current UN WPP release) and the same error/relError/horizon/bucket formulas on this page, so MAPE and mean bias are directly comparable across forecasters as arithmetic -- but each targets a different central scenario (see above), so a comparison also reflects each forecaster's scenario framing, not forecasting skill alone.
World Bank, OECD, and PRB population projections aren’t included here: they largely republish the UN medium variant rather than forecast independently.
Every source’s licence, coverage and API availability: Sources.