ATLAS · COMPARE
Prosperity & Family Size
As countries grow richer, do families really get smaller — and who breaks the rule?
Watch families shrink as the world sorts itself from poor to rich. The cloud tilts down to the right because the two move in opposite directions — that’s the shape of a strong correlation.
The two, blended into one map
Same data, a different read. Instead of one metric as colour and the other as bubbles, the two blend: each country is shaded by where it falls on both at once — so the map shows where fertility rate and gdp per capita are high together, and where they pull apart.
How strongly do they move together?
Across the 214 countries with both figures, fertility rate and gdp per capita move in opposite directions a strong amount — as one rises, the other tends to fall (correlation r = -0.78). That’s a clear, dependable pattern; the map below makes it visible at a glance.
Measured across the 214countries that have both figures, in each metric’s own scale (log scale where the map uses one). The scatter morph above plots these same countries; the dashed line is their best fit. Correlation is not causation — it only measures whether the two tend to track each other.
This is the demographic transition rendered as one image. On the blend, deep green marks high fertility with low income; deep blue marks wealth with small families; the two rarely share a colour. In Scatter, the dots fall along a clean downward slope — the clearest negative relationship in world demography. The countries to watch are the ones that refuse the slope: wealth that has not yet pulled family size down, or a poorer country already below replacement.
Who fits the pattern — and who breaks it
On the scatter, the rule-followers sit tight to the dashed line; the rule-breakers fly far from it. On the left, the countries that most clearly follow the relationship; on the right, the ones that most defy it.
Understand the underlying numbers
ATLAS · FIELD GUIDE
The Replacement Rate, and Why 2.1 Is the Most Important Number in Demography
Fertility rate decides whether a nation grows, holds steady, or slowly shrinks. A plain-language guide to what 'births per woman' means, why the magic number is about 2.1 rather than 2.0, and how to read the world map of a statistic that quietly shapes the next century.
ATLAS · FIELD GUIDE
GDP per Capita, and Why It Isn't the Same as How Rich People Are
GDP per capita is the standard yardstick for comparing how wealthy countries are — but it's an average that hides as much as it reveals. A plain-language guide to what it measures, why 'current US dollars' makes some comparisons misleading, and how to read the world map of it without overreaching.
Keep exploring
GEOGRAPHY ↔ DATA
Try another pairing — watch the whole world rearrange itself by the numbers.