Nepal Population Grid

What this grid is, and what it is not

Small-area projections are the demographic control totals; the raster only decides where inside each ward the people go. Each WorldPop pixel is assigned to the ward containing its centre, pixels are summed into grid cells, the weights are normalised within the ward, and the ward’s projected total is split across its cells by those weights. Conservation is guaranteed by construction and then checked: the national build reproduces every one of 6,743 ward totals with zero error, in each of the four years shown.

It carries no age and no sex. The downscaling distributed total population only, so any indicator that depends on age or sex — a dependency ratio, a share aged 65 and over — would be constant within a ward and would look like information it is not. popsym_grid_cell_varying() in popsymr refuses those by design.

It is residential. These are people where they live, not where they are during the day. Workers, pilgrims, traders and travellers are counted at home.

Displayed at 200 m by summing the underlying 100 m cells, on a quantile colour scale computed once on 2026 and then held fixed. Recomputing it per year would give each map its own scale, so a square could change colour while its population stayed put and the map would show the scale moving and call it growth. A linear scale would show almost nothing: the median inhabited cell holds under three people while the busiest holds hundreds. Uninhabited cells are left blank rather than coloured, because “nobody lives here” and “one person lives here” are different statements.

Sources

• National Statistics Office (2025) — National Population and Housing Census 2021: Population Projections for Nepal, 2021–2051. First edition. Kathmandu: National Statistics Office. ISBN 978-9937-9844-2-3. Samir KC was Lead Analyst. The projection framework the ward figures descend from.
• PopSyM Nepal — ward-level projections for 2026, 2031, 2041 and 2051, medium scenario, on the 2021 census base. Totals here are the sum of the ward control series, which for 2026 gives 30,323,061; the same scenario’s national projection file gives 30,048,358. That difference is carried, not reconciled, and is under discussion. These are the control totals: every ward’s projected population is preserved exactly, and the grid only decides where inside the ward it sits.
• WorldPop — Nepal 2025 constrained population, 100 m, release R2024B. Used only as a within-ward weight surface, never as a population total. Where WorldPop and the projection disagree on how many people a ward holds, the projection wins.
• popsymr — the grid contract, its schema and its validation. The national build passes popsym_validate_grid() structurally and under strict conservation against the ward projection.
• Ward boundaries — Survey Department of Nepal, via the ward geometry assembled in this repository, with the 82 wards whose polygons are not publicly released allocated within their palika residual. The boundaries themselves are not redistributed here; only results derived from them are shown, which is what the terms permit.
• Copernicus DEM and OpenStreetMap — district outlines are derived from the ward geometry above; city coordinates come from OpenStreetMap via Nominatim, © OpenStreetMap contributors, ODbL.
• Not shown: age, sex, or anything derived from them. The downscaling distributed total population only. It also shows residence, not daytime presence — workers, pilgrims, traders and travellers are counted at home.