Trinidad and Tobago: 12% more people than the UN expected in 2004 — mostly because migration added more people
The 2004 projection for 2023: 1.35M; the UN now estimates 1.5M, 158k more. The bars separate the sources of this gap.
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A population projection is built from four parts: how many people live there at the start, how many will be born, how many will die and how many more will arrive than leave. The UN has since estimated each part anew, which shows where the projection went wrong. Here the total missed, mostly because of one part. migration was expected to take away 72k people but added 6.5k; the UN later put the 2005 population 46.8k higher; 26.6k fewer people died than expected. Another source shows it too: people born abroad made up 3.3% of the population in 2005 and 7.5% in 2024 (UN International Migrant Stock, from censuses and registers).
A bar is how much one part moved the total against the projection: right means more people than projected, left means fewer; the number is the size of the move. More births and fewer deaths add people; fewer births and more deaths take them away. “2005 population higher / lower”: the UN later estimated the population the projection started from differently from what it assumed then. The last bar is the total; the parts add up to it within a small residual.
- UN 2004 projection for 2023
1.35M
- UN 2024 estimate
1.5M
- Population in 2005: in the projection → estimated now
1.31M → 1.35M
- Births 2005–2023: assumed → estimated now
327k → 334k
- Deaths 2005–2023: assumed → estimated now
216k → 189k
- Net migration 2005–2023, arrivals minus departures: assumed → estimated now
−72k → +6.5k
- Residual of the calculation
−0.9k
The UN 2004 projection for 2023 against the UN 2024 estimate. The gap is split along the population balance: the 2005 population (estimated now minus the one the projection started from), then births, deaths and net migration over 2005–2023 (estimated now minus assumed; for deaths the other way round, since more deaths mean fewer people). Residual −0.9k: rounding and the five-year periods of older projections. Chosen: a projection of at least 8 years off by 4% or more, where one part made at least 45% of the gap.
Both the projection and the current figure are UN estimates: in countries without full registration of births and deaths they come from a model, not a count.
A question for this picture
Which of these could have been known when the projection was made?