placestats

Fertility rate vs. Women's age at first marriage (census-based)

Fades after adjusting for income

Across 176 countries, Fertility rate and Women's age at first marriage (census-based) rise and fall together at r = -0.63 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to -0.09, which could easily be chance (q = 0.69, 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 women's age at first marriage (census-based), 21.9 to 27.9 years, fertility rate is 1.15 births per woman lower at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 0.133 births per woman.

Link before adjusting (r)-0.631p = 6.1e-21 · 176 countries
After adjusting for national income-0.090p = 0.239 · likely range [-0.23, +0.06]
p, allowing for regions0.391standard error 0.097 · 7 regions
Check for luck (q)0.687across 14,952 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.

Fertility rate · births per womanlink with income -0.81 · proxy
Women's age at first marriage (census-based) · yearslink with income +0.75 · high

Both of these rise and fall closely with national income, so a strong link between them before adjusting was close to certain. Read the adjusted figure, not the first one.

“Link with income” is how closely each measure tracks GDP per person across countries, from −1 to +1.

Every country as a dot

Fertility rate · births per woman →Women's age at first marriage (census-based) · years →0.5826.031734Aruba: 1.61 births per woman, 28.5 yearsAfghanistan: 4.76 births per woman, 21.5 yearsAngola: 5.05 births per woman, 21.5 yearsAlbania: 1.34 births per woman, 24.2 yearsArgentina: 1.5 births per woman, 24.6 yearsArmenia: 1.7 births per woman, 24.2 yearsAustralia: 1.48 births per woman, 29.9 yearsAustria: 1.31 births per woman, 27.1 yearsAzerbaijan: 1.43 births per woman, 24.2 yearsBurundi: 4.79 births per woman, 22.8 yearsBelgium: 1.44 births per woman, 26.3 yearsBenin: 4.48 births per woman, 20.7 yearsBurkina Faso: 4.11 births per woman, 20 yearsBangladesh: 2.14 births per woman, 18.8 yearsBulgaria: 1.72 births per woman, 32.6 yearsBahrain: 1.8 births per woman, 26.9 yearsBahamas, The: 1.37 births per woman, 27.9 yearsBosnia and Herzegovina: 1.49 births per woman, 25.7 yearsBelarus: 1.22 births per woman, 22.5 yearsBelize: 2.02 births per woman, 20.5 yearsBermuda: 1.41 births per woman, 31.9 yearsBolivia: 2.52 births per woman, 24 yearsBrazil: 1.61 births per woman, 23.9 yearsBarbados: 1.71 births per woman, 17 yearsBrunei Darussalam: 1.73 births per woman, 26.1 yearsBhutan: 1.45 births per woman, 23.8 yearsBotswana: 2.7 births per woman, 22.9 yearsCentral African Republic: 5.95 births per woman, 17.3 yearsCanada: 1.25 births per woman, 27.2 yearsSwitzerland: 1.29 births per woman, 30.9 yearsChile: 1.14 births per woman, 27.4 yearsChina: 1.01 births per woman, 25.4 yearsCote d'Ivoire: 4.23 births per woman, 23 yearsCameroon: 4.26 births per woman, 22.2 yearsCongo, Dem. Rep.: 5.98 births per woman, 20.9 yearsCongo, Rep.: 4.11 births per woman, 21.9 yearsColombia: 1.63 births per woman, 22.7 yearsComoros: 3.82 births per woman, 22.6 yearsCosta Rica: 1.32 births per woman, 26.4 yearsCayman Islands: 1.52 births per woman, 28 yearsCyprus: 1.38 births per woman, 26.4 yearsCzechia: 1.36 births per woman, 32.4 yearsGermany: 1.36 births per woman, 31.7 yearsDjibouti: 2.62 births per woman, 29.9 yearsDenmark: 1.47 births per woman, 31.9 yearsDominican Republic: 2.22 births per woman, 21.5 yearsAlgeria: 2.72 births per woman, 28.2 yearsEcuador: 1.81 births per woman, 21.8 yearsEgypt, Arab Rep.: 2.73 births per woman, 22.3 yearsSpain: 1.1 births per woman, 27.7 yearsEstonia: 1.18 births per woman, 33.6 yearsEthiopia: 3.91 births per woman, 21.3 yearsFinland: 1.25 births per woman, 30.7 yearsFrance: 1.61 births per woman, 32 yearsFaroe Islands: 1.91 births per woman, 31 yearsMicronesia, Fed. Sts.: 2.74 births per woman, 25.3 yearsGabon: 3.59 births per woman, 22.9 yearsUnited Kingdom: 1.55 births per woman, 27 yearsGeorgia: 1.8 births per woman, 22.8 yearsGhana: 3.34 births per woman, 23.7 yearsGuinea: 4.13 births per woman, 19.8 yearsGambia, The: 3.91 births per woman, 21.5 yearsGuinea-Bissau: 3.76 births per woman, 24.1 yearsEquatorial Guinea: 4.12 births per woman, 20.5 yearsGreece: 1.24 births per woman, 29.2 yearsGreenland: 1.71 births per woman, 32.9 yearsGuatemala: 2.29 births per woman, 22.7 yearsGuyana: 2.4 births per woman, 19.2 yearsHong Kong SAR, China: 0.841 births per woman, 29.9 yearsHonduras: 2.48 births per woman, 21.2 yearsCroatia: 1.46 births per woman, 27.4 yearsHaiti: 2.63 births per woman, 24.9 yearsHungary: 1.41 births per woman, 32.9 yearsIndonesia: 2.12 births per woman, 22.4 yearsIndia: 1.96 births per woman, 21.4 yearsIreland: 1.47 births per woman, 32.4 yearsIran, Islamic Rep.: 1.68 births per woman, 23.1 yearsIraq: 3.22 births per woman, 22.7 yearsIceland: 1.56 births per woman, 32.4 yearsIsrael: 2.87 births per woman, 26.2 yearsItaly: 1.18 births per woman, 32.2 yearsJamaica: 1.35 births per woman, 25.3 yearsJordan: 2.6 births per woman, 24.6 yearsJapan: 1.15 births per woman, 29.2 yearsKazakhstan: 2.98 births per woman, 22.4 yearsKenya: 3.17 births per woman, 21.9 yearsKyrgyz Republic: 2.6 births per woman, 21.2 yearsCambodia: 2.55 births per woman, 21.6 yearsKiribati: 3.12 births per woman, 21.6 yearsKorea, Rep.: 0.748 births per woman, 31.5 yearsKuwait: 1.56 births per woman, 25.7 yearsLao PDR: 2.4 births per woman, 20.7 yearsLiberia: 3.86 births per woman, 22.6 yearsSt. Lucia: 1.39 births per woman, 21.9 yearsSri Lanka: 1.95 births per woman, 23.9 yearsLesotho: 2.66 births per woman, 22.2 yearsLithuania: 1.11 births per woman, 32.7 yearsLuxembourg: 1.25 births per woman, 30.7 yearsLatvia: 1.24 births per woman, 30.4 yearsMacao SAR, China: 0.582 births per woman, 30.3 yearsMorocco: 2.21 births per woman, 24.4 yearsMoldova: 1.73 births per woman, 25 yearsMaldives: 1.56 births per woman, 22.5 yearsMexico: 1.89 births per woman, 23.2 yearsMarshall Islands: 2.86 births per woman, 24.2 yearsNorth Macedonia: 1.4 births per woman, 25.5 yearsMali: 5.51 births per woman, 18.8 yearsMalta: 1.01 births per woman, 28 yearsMyanmar: 2.1 births per woman, 22.9 yearsMontenegro: 1.8 births per woman, 26.3 yearsMongolia: 2.5 births per woman, 23 yearsMozambique: 4.69 births per woman, 18.7 yearsMauritania: 4.63 births per woman, 21.8 yearsMauritius: 1.44 births per woman, 23.9 yearsMalawi: 3.59 births per woman, 20.4 yearsMalaysia: 1.54 births per woman, 25.7 yearsNamibia: 3.21 births per woman, 30.3 yearsNiger: 5.93 births per woman, 17.2 yearsNigeria: 4.38 births per woman, 21.2 yearsNicaragua: 2.21 births per woman, 21.1 yearsNetherlands: 1.43 births per woman, 32.4 yearsNorway: 1.45 births per woman, 32.1 yearsNepal: 1.96 births per woman, 20.1 yearsOman: 2.51 births per woman, 25.6 yearsPakistan: 3.55 births per woman, 23.2 yearsPanama: 2.11 births per woman, 21 yearsPeru: 1.97 births per woman, 23.3 yearsPhilippines: 1.89 births per woman, 23.4 yearsPalau: 1.88 births per woman, 28.5 yearsPapua New Guinea: 3.07 births per woman, 21.4 yearsPoland: 1.14 births per woman, 26.6 yearsPuerto Rico (US): 0.92 births per woman, 29.2 yearsPortugal: 1.41 births per woman, 30.1 yearsParaguay: 2.42 births per woman, 21.9 yearsWest Bank and Gaza: 3.25 births per woman, 22.1 yearsRomania: 1.39 births per woman, 25.9 yearsRussian Federation: 1.42 births per woman, 24.4 yearsRwanda: 3.65 births per woman, 24.3 yearsSaudi Arabia: 2.31 births per woman, 26.6 yearsSudan: 4.26 births per woman, 21.9 yearsSenegal: 3.77 births per woman, 22.2 yearsSingapore: 0.97 births per woman, 27.9 yearsSolomon Islands: 3.51 births per woman, 22.4 yearsSierra Leone: 3.7 births per woman, 23.1 yearsEl Salvador: 1.77 births per woman, 22.6 yearsSan Marino: 1.16 births per woman, 31.3 yearsSerbia: 1.64 births per woman, 26.6 yearsSao Tome and Principe: 3.6 births per woman, 21 yearsSuriname: 2.23 births per woman, 29.3 yearsSlovak Republic: 1.46 births per woman, 31 yearsSlovenia: 1.52 births per woman, 34 yearsSweden: 1.43 births per woman, 31 yearsEswatini: 2.72 births per woman, 26.5 yearsSint Maarten (Dutch part): 1.44 births per woman, 28 yearsChad: 6.03 births per woman, 18.8 yearsTogo: 4.12 births per woman, 21.3 yearsThailand: 1.2 births per woman, 22.5 yearsTajikistan: 3.04 births per woman, 20.7 yearsTurkmenistan: 2.66 births per woman, 23.5 yearsTimor-Leste: 2.63 births per woman, 23 yearsTonga: 3.1 births per woman, 25.3 yearsTrinidad and Tobago: 1.54 births per woman, 29.2 yearsTunisia: 1.82 births per woman, 28.2 yearsTurkiye: 1.48 births per woman, 23.4 yearsTanzania: 4.54 births per woman, 21 yearsUganda: 4.17 births per woman, 20.7 yearsUkraine: 0.988 births per woman, 23 yearsUruguay: 1.4 births per woman, 23 yearsUnited States: 1.63 births per woman, 27.5 yearsSt. Vincent and the Grenadines: 1.76 births per woman, 21.2 yearsVirgin Islands (U.S.): 1.97 births per woman, 30.9 yearsViet Nam: 1.9 births per woman, 22.8 yearsSamoa: 3.8 births per woman, 23.8 yearsSouth Africa: 2.21 births per woman, 27.2 yearsZambia: 4.04 births per woman, 21.8 yearsZimbabwe: 3.67 births per woman, 21.1 yearsBGDBRBCAFCODESTKORLTUNAMNERSVNTCDUKR

best-fit line line after adjusting

Four ways to measure the link

MethodrpCountries
Standard (Pearson), not adjusted-0.6316.1e-21176
By rank (Spearman), not adjusted-0.6803.1e-25176
Standard (Pearson), adjusted for national income-0.0900.239176
By rank (Spearman), adjusted for national income-0.1930.011176

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 176 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: +0.542 (a minus sign means it grew).

How solid is it?

Leaving out one country at a time, r ranges from -0.103 (without BRB) to -0.049 (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 (+0.040).

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.

nr
East Asia & Pacific26-0.08
Europe & Central Asia50-0.12
Latin America & Caribbean32-0.31
Middle East, North Africa, Afghanistan & Pakistan17-0.34
Sub-Saharan Africa42-0.54

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.

nr
Poorest third59-0.34
Middle third58+0.01
Richest third59-0.45

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.

nr
Christians105-0.09
Muslims42-0.34

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.

nr
France22-0.53
Never a European colony20-0.10
Spain20-0.54
United Kingdom50-0.01

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 = -0.075 after dropping 4 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 30years. 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 = +0.200) but mostly disappears in year-to-year changes (r = +0.047). That points to slow trends particular to each country, not the two measures moving together from year to year.

Across countries (adjusted)-0.090for comparison
Within countries-0.165each country vs itself
…and vs the same year elsewhere+0.200q = 0.001 · 123 countries
Year-on-year changes+0.047q = 0.613
The direction flips. Comparing each country only with itself gives -0.16. Also taking out what happened to the whole world each year gives +0.20. So the first figure was picking up a trend both measures share with worldwide progress, not a link between them.
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.

1,180 country-years (one country in one year), 123 countries, 1990–2019, about 10 years each on average. Share of the variation that happens within countries over time: 14% for Fertility rate, 6% for Women's age at first marriage (census-based). 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

0.30−0.3-100+10years Women's age at first marriage (census-based) trails Fertility rate →lag -10: r = 0.286 (n = 969)lag -9: r = 0.283 (n = 1,016)lag -8: r = 0.284 (n = 1,095)lag -7: r = 0.283 (n = 1,140)lag -6: r = 0.276 (n = 1,179)lag -5: r = 0.274 (n = 1,180)lag -4: r = 0.265 (n = 1,180)lag -3: r = 0.254 (n = 1,180)lag -2: r = 0.239 (n = 1,180)lag -1: r = 0.223 (n = 1,180)lag +0: r = 0.200 (n = 1,180)lag +1: r = 0.184 (n = 1,127)lag +2: r = 0.167 (n = 1,057)lag +3: r = 0.175 (n = 1,021)lag +4: r = 0.174 (n = 986)lag +5: r = 0.162 (n = 946)lag +6: r = 0.173 (n = 902)lag +7: r = 0.156 (n = 850)lag +8: r = 0.136 (n = 808)lag +9: r = 0.151 (n = 773)lag +10: r = 0.136 (n = 708)

Same year (lag 0): +0.200. 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.

This curve peaks at the edge of the window (lag -10), so it is still drifting where the search stops. That pattern usually reflects a slow trend left over in the data, not a link with real timing. The peak value should not be read as the “true” link at the right lag.

The data


births per woman
years		Years
Chad TCD6.0318.82024, 2015
Congo, Dem. Rep. COD5.9820.92024, 2014
Central African Republic CAF5.9517.32024, 2010
Niger NER5.9317.22024, 2015
Mali MLI5.5118.82024, 2018
Angola AGO5.0521.52024, 2016
Burundi BDI4.7922.82024, 2016
Afghanistan AFG4.7621.52024, 2015
Mozambique MOZ4.6918.72024, 2017
Mauritania MRT4.6321.82024, 2015
Tanzania TZA4.54212024, 2016
Benin BEN4.4820.72024, 2018
Nigeria NGA4.3821.22024, 2013
Sudan SDN4.2621.92024, 2014
Cameroon CMR4.2622.22024, 2014

World Bank, World Development Indicators
World Bank Gender Statistics, from UN Population Division, World Marriage Data

Sources

Fertility rate

Fertility rate, total (births per woman)

World Bank · CC BY 4.0 · updated quarterly

Women's age at first marriage (census-based)

Age at first marriage, female

World Bank · CC BY 4.0 · updated annual

The average age at which women first marry. It is worked out from census and survey counts of how many women in each age group have never married, by the UN Population Division (World Marriage Data), so it covers far more countries than registered marriages do. Most countries have a figure only every few years, and the series ends in 2019. No "better" direction is set.

How this was computed

Data used: most recent value in 2010-2025; values come from 2010–2024. 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 14,952 pairs at once, using the Benjamini–Hochberg method. Underlying data last updated DYB 2024. How the country data works · explore Fertility rate and Women's age at first marriage (census-based)

This page shows that two measures go together. It does not show that Fertility rate changes Women's age at first marriage (census-based), or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.

More links with Fertility rate or Women's age at first marriage (census-based)