How comparisons are built.

Geometry

The base country geometry is derived from Natural Earth 1:50m Admin 0 country boundaries. The geometry is treated as a visualization layer, not as a legal statement about borders or sovereignty.

The default map uses a Mercator projection because it is familiar to most users. Area comparisons include latitude-aware reprojection when country outlines are moved across the map.

Additive metrics

Metrics with additive totals, such as population, GDP, emissions, production, and land area, can be aggregated across country groups. Their comparison bars use group totals and each country segment's contribution to the opposite group.

For non-area additive metrics, cartogram sizing is based on the metric value itself, not on Mercator map area.

Rate and index metrics

Rates, percentages, per-person values, indexes, and similar non-additive metrics are not summed. The site shows them with a value gradient and a legend instead of group totals.

When countries are selected, the gradient is scaled to the selected countries so close comparisons remain visible.

Missing data

Countries without a value for the selected metric remain visible but are marked with a neutral hatched treatment. They are excluded from ranks, aggregates, and cartogram scaling for that metric.

Reference years

Metrics are presented with their source and reference year when available. A reference year is the year used for comparison; it may differ across metrics depending on source availability.