How country comparisons are built.

Geometry

The base map geometry is derived from Natural Earth 1:50m Admin 0 country boundaries. The geometry is frozen and used only as a visualization layer. It is not a legal statement about borders, sovereignty, jurisdiction, names, or territorial disputes.

The default world map uses a Mercator projection because it is familiar to most users. For land area comparison, moved country outlines are adjusted for latitude so a country dragged far north or south changes shape in a way that is consistent with the projection.

Additive metrics

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

For non-area additive metrics, cartogram sizing is based on the metric value itself, not on the country's apparent Mercator map area. Countries with no value for the selected metric stay visible as no-data countries but are excluded from totals and cartogram scaling.

The group calculation is the sum of available member observations. Coverage is retained alongside the result, so a five-country group with four observations is identified as four of five rather than silently treating the missing country as zero.

Rate and index metrics

Rates, percentages, per-person values, indexes, and similar non-additive metrics are not summed. GDP per capita, population density, life expectancy, internet use, and percentage indicators are examples where group totals would be misleading.

For those metrics, the site keeps countries in their geographic positions and uses a color gradient with a numeric legend. 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.

How to interpret the map

Compare Countries is designed for visual exploration. A map view can reveal broad differences quickly, but the exact number, source, reference year, and coverage note should be checked before citing a figure. For formal analysis, use the original source named in the app.