Across 163 countries, Adolescent fertility and Gini index rise and fall together at r = +0.45 (on a scale from −1 to +1, where 0 means no link). It holds up almost unchanged when only countries with similar income (GDP per person) are compared (r = +0.38, q = 0.0025, allowing for the many pairs tested). Caution: direction is not consistent across regions.
Comparing countries across the middle half of gini index, 31 to 40 points, adolescent fertility is worse by 22.3 births per 1,000 women aged 15-19 at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 12.8 births per 1,000 women aged 15-19.
Link before adjusting (r)+0.453p = 1.2e-9 · 163 countries
After adjusting for national income+0.381p = 5.9e-7 · likely range [+0.24, +0.51]
p, allowing for regions0.008standard error 0.096 · 7 regions
Check for luck (q)0.003across 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.
Adolescent fertility · births per 1,000 women aged 15-19link with income -0.81 · proxy
Gini index · index (0-100)link with income -0.34 · 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
+0.453
1.2e-9
163
By rank (Spearman), not adjusted
+0.509
4.0e-12
163
Standard (Pearson), adjusted for national income
+0.381
5.9e-7
163
By rank (Spearman), adjusted for national income
+0.432
9.6e-9
163
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 163 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: +0.073 (a minus sign means it grew).
How solid is it?
Leaving out one country at a time, r ranges from +0.354 (without AGO) to +0.399 (without GIN). 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: AGO (-0.027).
Fragile: this link may not hold up.
direction is not consistent across regions
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
23
+0.10
Europe & Central Asia
47
+0.12
Latin America & Caribbean
24
+0.31
Middle East, North Africa, Afghanistan & Pakistan
16
-0.31
Sub-Saharan Africa
45
+0.14
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
55
+0.40
Middle third
54
+0.46
Richest third
54
+0.32
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
103
+0.47
Muslims
40
-0.08
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
+0.24
Never a European colony
16
+0.20
Spain
20
+0.13
United Kingdom
48
+0.46
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 = +0.371 after dropping 8 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 35years. So a link here can’t come from anything about a country that stays the same, such as its history, geography, institutions or culture.
The link shows up within countries over time (r = +0.179) but mostly disappears in year-to-year changes (r = -0.031). That points to slow trends particular to each country, not the two measures moving together from year to year.
Across countries (adjusted)+0.381for comparison
Within countries+0.326each country vs itself
…and vs the same year elsewhere+0.179q = 0.010 · 120 countries
Year-on-year changes-0.031q = 0.578
Read with care.
Almost all of the second indicator's variation is between countries, so the within-country estimate rests on a small part of the data.
2,107 country-years (one country in one year), 120 countries, 1990–2024, about 18 years each on average. Share of the variation that happens within countries over time: 14% for Adolescent fertility, 8% for Gini index. The margins of error allow for each country appearing many times, and for each year’s value being close to the year before.
Year-to-year changes are a cautious test, not a final answer. Looking only at changes from one year to the next removes each country’s own trends. But it also makes measurement mistakes louder, which pulls the results toward zero. A near-zero result here is weak evidence of no link, not proof.
With one measure years behind the other
Same year (lag 0): +0.179. A peak away from zero does not show which comes first. These series change slowly — this year’s value is close to last year’s. That makes the curve smooth and nearly symmetric, whatever produced the data. Even a sharp peak at one lag (a gap of some years) would not prove that one measure changes the other.
The largest value on this curve (+0.25 at lag -9) is higher than the same-year one by 0.07. That gap is not a finding. It is the largest of 21 closely related estimates, and picking the biggest of many tests always makes it look bigger. That is exactly why nothing on this site is ranked or chosen by lag.
The data
births per 1,000 women aged 15-19
index (0-100)
Years
Central African Republic CAF
161
43
2024, 2021
Equatorial Guinea GNQ
153
38.5
2024, 2022
Mozambique MOZ
152
49.6
2024, 2022
Niger NER
142
32.9
2024, 2021
Angola AGO
139
51.3
2024, 2018
Mali MLI
136
35.7
2024, 2021
Chad TCD
132
37.4
2024, 2022
Madagascar MDG
129
36.8
2024, 2021
Liberia LBR
125
35.3
2024, 2016
Guinea GIN
117
29.6
2024, 2018
Zambia ZMB
115
51.5
2024, 2022
Malawi MWI
113
38.5
2024, 2019
Tanzania TZA
113
40.5
2024, 2018
Congo, Rep. COG
108
48.9
2024, 2011
Cameroon CMR
105
42.2
2024, 2021
World Bank, World Development Indicators World Bank, World Development Indicators
Sparse and uneven: most countries report only every few years, and coverage is thinnest where inequality is highest. Be wary of comparisons that match Gini with other measures year by year.
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 7 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 Adolescent fertility and Gini index
This page shows that two measures go together. It does not show that Adolescent fertility changes Gini index, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.
More links with Adolescent fertility or Gini index