Human capital (PWT) vs. Married by 18
Fades after adjusting for income
Across 101 countries, Human capital (PWT) and Married by 18 rise and fall together at r = -0.68 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to -0.35, which could easily be chance (q = 0.052, 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 human capital (PWT), 2.02 to 2.99 points, married by 18 is better by 14.8% of women aged 20-24 at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 9.91% of women aged 20-24.
Link before adjusting (r)-0.684p = 3.2e-15 · 101 countries
After adjusting for national income-0.349p = 0.000 · likely range [-0.51, -0.16]
p, allowing for regions0.006standard error 0.076 · 6 regions
Check for luck (q)0.052across 18,622 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.
Human capital (PWT) · index (1 = no schooling)link with income +0.82 · proxy
Married by 18 · % of women aged 20-24link with income -0.60 · moderate
“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 | -0.684 | 3.2e-15 | 101 |
| By rank (Spearman), not adjusted | -0.685 | 3.0e-15 | 101 |
| Standard (Pearson), adjusted for national income | -0.349 | 0.000 | 101 |
| By rank (Spearman), adjusted for national income | -0.342 | 0.001 | 101 |
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 101 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: +0.335 (a minus sign means it grew).
How solid is it?
Leaving out one country at a time, r ranges from -0.387 (without SWZ) to -0.311 (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: GUY (+0.039).
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 | ||
|---|---|---|---|
| Europe & Central Asia | 17 | -0.70 | |
| Latin America & Caribbean | 22 | -0.33 | |
| Sub-Saharan Africa | 35 | -0.28 |
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 | 34 | -0.31 | |
| Middle third | 33 | -0.28 | |
| Richest third | 34 | -0.52 |
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 | 60 | -0.25 | |
| Muslims | 28 | -0.51 |
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 | 19 | -0.42 | |
| Never a European colony | 13 | -0.80 | |
| Spain | 18 | -0.32 | |
| United Kingdom | 33 | -0.12 |
By official ideology
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 | ||
|---|---|---|---|
| Nationalist | 16 | -0.37 | |
| No strong official ideology | 65 | -0.48 |
By party system
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 | ||
|---|---|---|---|
| A few parties banned | 19 | -0.60 | |
| No parties banned | 70 | -0.37 |
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 = -0.331 after dropping 1 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
index (1 = no schooling) | % of women aged 20-24 | Years | |
|---|---|---|---|
| Israel ISR | 3.99 | 0.8% | 2023, 2022 |
| United Kingdom GBR | 3.85 | 0% | 2023, 2021 |
| Norway NOR | 3.75 | 0% | 2023, 2022 |
| Denmark DNK | 3.67 | 0.7% | 2023, 2021 |
| Finland FIN | 3.6 | 0.1% | 2023, 2017 |
| Kyrgyz Republic KGZ | 3.57 | 9.2% | 2023 |
| Serbia SRB | 3.53 | 5.5% | 2023, 2019 |
| Lithuania LTU | 3.41 | 0.2% | 2023, 2022 |
| Singapore SGP | 3.4 | 0.1% | 2023, 2025 |
| Kazakhstan KAZ | 3.39 | 6.1% | 2023, 2024 |
| Romania ROU | 3.35 | 6.9% | 2023, 2021 |
| Russian Federation RUS | 3.34 | 6.2% | 2023, 2017 |
| Ukraine UKR | 3.32 | 9.1% | 2023, 2012 |
| Chile CHL | 3.24 | 0% | 2023, 2024 |
| Moldova MDA | 3.18 | 12.2% | 2023, 2012 |
Feenstra, Robert C., Robert Inklaar and Marcel P. Timmer (2015), "The Next Generation of the Penn World Table", American Economic Review, 105(10), 3150-3182, www.ggdc.net/pwt. Data: Penn World Table version 11.0, Groningen Growth and Development Centre, doi:10.34894/FABVLR.
World Bank, World Development Indicators
Sources
Human capital (PWT)
Human capital index, from years of schooling (Penn World Table)
Groningen Growth and Development Centre, University of Groningen · via DataverseNL · CC BY 4.0 · updated irregular (new versions every few years)
"Human capital" means the skills and knowledge workers bring to their jobs. This index measures it from schooling alone. It starts from how many years adults spent in school, then counts the early years for more than the later ones, following studies of how much higher pay tends to be with each extra year. A score of 1 means no schooling; the US is about 3.8. It uses the same schooling figures as mean years of schooling, so the two are close by construction. For that reason it is left out of the education score, which already counts years of schooling.
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.
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 18,622 pairs at once, using the Benjamini–Hochberg method. Underlying data last updated V-Dem v16; V-Party v2. How the country data works · explore Human capital (PWT) and Married by 18
This page shows that two measures go together. It does not show that Human capital (PWT) changes Married by 18, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.
More links with Human capital (PWT) or Married by 18
- Married by 18 vs Women's age at first marriage (census-based) before -0.74 → after adjusting -0.61
- Education score vs Married by 18 before -0.72 → after adjusting -0.48
- HDI vs Married by 18 before -0.70 → after adjusting -0.47
- Married by 18 vs Mean years of schooling before -0.70 → after adjusting -0.45
- 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
- Human capital (PWT) vs One-person households before +0.72 → after adjusting +0.42
- Married by 18 vs PISA maths before -0.59 → after adjusting -0.41