Married by 18 vs. Mean years of schooling
Fades after adjusting for income
Across 134 countries, Married by 18 and Mean years of schooling rise and fall together at r = -0.70 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to -0.45, which could easily be chance (q = 0.054, allowing for the many pairs tested, and allowing for countries in the same region being alike). So the first figure mostly shows richer countries differing from poorer ones, not a link between these two things.
Comparing countries across the middle half of mean years of schooling, 6.02 to 10.8 years, married by 18 is better by 15.6% of women aged 20-24 at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 12.6% of women aged 20-24.
Link before adjusting (r)-0.699p = 5.7e-21 · 134 countries
After adjusting for national income-0.450p = 5.3e-8 · likely range [-0.58, -0.30]
p, allowing for regions0.012standard error 0.116 · 6 regions
Check for luck (q)0.054across 12,497 pairs
How to read these.r runs from −1 (one goes up as the other goes down) to +1 (they rise together), and 0 means no link. Adjusting for national income means comparing countries with the same GDP per person, so differences in wealth can’t explain the link. Income is used in percentage terms, since an extra $1,000 means more to a poor country than to a rich one. p is how likely a link this strong would be if there were really none. Below 0.05 means it is unlikely to be chance. Very small values are written in short form: 1.1e-32 means a decimal point followed by 31 zeros and then 11, so very close to zero. The likely range is where the true figure probably lies, and a range that crosses zero means the link could easily be chance. Countries in the same region tend to resemble each other, so the third figure allows for that, which gives a fairer p. The standard error is the typical size of the error in r. Finally, testing this many pairs means some will look strong by luck alone. A q below 0.05 means this link is unlikely to be one of those.
Married by 18 · % of women aged 20-24link with income -0.60 · moderate
Mean years of schooling · yearslink with income +0.82 · proxy
“Link with income” is how closely each measure tracks GDP per person across countries, from −1 to +1.
Every country as a dot
best-fit line line after adjusting
Four ways to measure the link
| Method | r | p | Countries |
|---|---|---|---|
| Standard (Pearson), not adjusted | -0.699 | 5.7e-21 | 134 |
| By rank (Spearman), not adjusted | -0.696 | 1.0e-20 | 134 |
| Standard (Pearson), adjusted for national income | -0.450 | 5.3e-8 | 134 |
| By rank (Spearman), adjusted for national income | -0.445 | 7.7e-8 | 134 |
The rank version uses only each country’s place in line, from lowest to highest, so a few extreme countries count for less. The adjusted and unadjusted versions use the same 134 countries: those that report both measures and GDP per person. So the gap between them comes from the adjustment, not from a change in which countries are counted. Drop in the size of r after adjusting: +0.249 (a minus sign means it grew).
How solid is it?
Leaving out one country at a time, r ranges from -0.478 (without DJI) to -0.424 (without GUY). The bar above shows that range on a scale from −1 to +1, with the solid line at the full result. The single country that moves r most: DJI (-0.028).
Within each region
Countries are not separate, unrelated cases, and neighbors share a lot. A link that holds inside each region is far more believable than one that shows up only when comparing regions.
| n | r | ||
|---|---|---|---|
| East Asia & Pacific | 20 | -0.65 | |
| Europe & Central Asia | 25 | -0.65 | |
| Latin America & Caribbean | 24 | -0.31 | |
| Middle East, North Africa, Afghanistan & Pakistan | 17 | -0.13 | |
| Sub-Saharan Africa | 42 | -0.48 |
By income third
If the link shows up only in the richest third of countries, it is a feature of rich countries, not a general pattern.
| n | r | ||
|---|---|---|---|
| Poorest third | 45 | -0.57 | |
| Middle third | 44 | -0.25 | |
| Richest third | 45 | -0.53 |
By largest religious group
Countries grouped by a label they share, such as main religion, rather than by a number. Groups of fewer than twelve countries are not shown. These groups differ in income, region and history all at once. So a gap between them is a place to start asking questions, not an answer.
| n | r | ||
|---|---|---|---|
| Christians | 76 | -0.43 | |
| Muslims | 42 | -0.48 |
By last european coloniser
Countries grouped by a label they share, such as main religion, rather than by a number. Groups of fewer than twelve countries are not shown. These groups differ in income, region and history all at once. So a gap between them is a place to start asking questions, not an answer.
| n | r | ||
|---|---|---|---|
| France | 24 | -0.38 | |
| Never a European colony | 19 | -0.73 | |
| Spain | 19 | -0.21 | |
| United Kingdom | 43 | -0.41 |
Without outliers (countries far outside the middle half of countries on either measure, by more than one and a half times the width of that middle half): r = -0.436 after dropping 3 countries.
Two series, one country
Both measures over the years for one country you pick. The two charts are stacked so they share only the years along the bottom.
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Over time, within countries
Everything above compares countries with each other at one moment. This section compares each country only with itself over 0years. So a link here can’t come from anything about a country that stays the same, such as its history, geography, institutions or culture.
Not enough history inside each country to look at this over time. That needs countries measured for several years in a row, and at least one of these measures is measured too rarely.
The data
% of women aged 20-24 | years | Years | |
|---|---|---|---|
| Niger NER | 76.3% | 1.41 | 2012, 2023 |
| Central African Republic CAF | 61% | 3.99 | 2019, 2023 |
| Chad TCD | 60.6% | 2.33 | 2019, 2023 |
| Mali MLI | 48.5% | 1.63 | 2024, 2023 |
| Mozambique MOZ | 48.4% | 4.59 | 2023 |
| Bangladesh BGD | 47.2% | 6.79 | 2025, 2023 |
| Guinea GIN | 46.5% | 2.49 | 2018, 2023 |
| Ethiopia ETH | 40.3% | 2.4 | 2016, 2023 |
| Madagascar MDG | 38.8% | 4.59 | 2021, 2023 |
| Malawi MWI | 38.7% | 5.24 | 2024, 2023 |
| Burkina Faso BFA | 38.2% | 2.27 | 2021, 2023 |
| Mauritania MRT | 36.6% | 4.85 | 2021, 2023 |
| Suriname SUR | 36% | 8.43 | 2018, 2023 |
| Nicaragua NIC | 35.2% | 9.93 | 2012, 2023 |
| Nepal NPL | 34.9% | 4.5 | 2022, 2023 |
World Bank, World Development Indicators
United Nations Development Programme, Human Development Report 2025
Sources
Married by 18
Women who were first married by age 18 (% of women ages 20-24)
UNICEF · CC BY 4.0 · updated quarterly
From household surveys, mostly in lower-income countries, and only in years a survey ran. No year reaches sixty countries, so the latest value used is up to a decade old for some. Rich countries rarely report it at all, which shapes any link with income.
Mean years of schooling
Mean years of schooling, adults aged 25 and over
United Nations Development Programme, Human Development Report Office · via Our World in Data · CC BY 3.0 IGO · updated annual
The schooling adults actually completed, decades ago for most of them. Expected schooling looks ahead at children; this looks back at adults. It is the one to read for the education of the workforce rather than of children.
How this was computed
Data used: most recent value in 2010-2025; values come from 2010–2025. To adjust for income, each measure is first predicted from GDP per person (in percentage terms, on a log scale) with a straight-line fit. Only what is left over is then compared. This is called a partial correlation. The line is drawn the standard way (ordinary least squares), which picks the line that comes closest to all the countries at once. The error margins allow for countries in the same region resembling each other, using 6 World Bank regions. The q-value corrects for testing all 12,497 pairs at once, using the Benjamini–Hochberg method. Underlying data last updated DYB 2024. How the country data works · explore Married by 18 and Mean years of schooling
This page shows that two measures go together. It does not show that Married by 18 changes Mean years of schooling, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.
More links with Married by 18 or Mean years of schooling
- Education score vs Married by 18 before -0.72 → after adjusting -0.48
- Family benefits spending vs Mean years of schooling before +0.56 → after adjusting +0.47
- HDI vs Married by 18 before -0.70 → after adjusting -0.47
- Gender Inequality Index vs Married by 18 before +0.70 → after adjusting +0.44
- Married by 18 vs Skilled birth attendance before -0.64 → after adjusting -0.43
- Married by 18 vs PISA maths before -0.59 → after adjusting -0.41
- Mean years of schooling vs PISA maths before +0.72 → after adjusting +0.41
- Informal employment vs Mean years of schooling before -0.83 → after adjusting -0.41