placestats

Median age vs. PISA science

Holds up after adjusting for income

Across 87 countries, Median age and PISA science rise and fall together at r = +0.72 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to +0.50 (q = 0.032, allowing for the many pairs tested). Much of the first figure is that both measures rise with national income, but a moderate positive link remains.

Comparing countries across the middle half of pisa science, 403 to 491 PISA points, median age is 7.77 years higher at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 6.83 years.

Link before adjusting (r)+0.716p = 6.3e-15 · 87 countries
After adjusting for national income+0.496p = 1.2e-6 · likely range [+0.32, +0.64]
p, allowing for regions0.006standard error 0.092 · 5 regions
Check for luck (q)0.032across 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.

Median age · yearslink with income +0.86 · proxy
PISA science · PISA pointslink with income +0.78 · 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

Median age · years →PISA science · PISA points →19.849347561Albania: 36.3 years, 376 PISA pointsUnited Arab Emirates: 31.2 years, 432 PISA pointsArgentina: 32.1 years, 406 PISA pointsAustralia: 37.8 years, 507 PISA pointsAustria: 43.1 years, 491 PISA pointsBelgium: 41.4 years, 491 PISA pointsBulgaria: 44.3 years, 421 PISA pointsBosnia and Herzegovina: 44.9 years, 398 PISA pointsBelarus: 40.5 years, 471 PISA pointsBrazil: 33.9 years, 403 PISA pointsBrunei Darussalam: 31.8 years, 446 PISA pointsCanada: 40.3 years, 515 PISA pointsSwitzerland: 42.3 years, 503 PISA pointsChile: 36 years, 444 PISA pointsColombia: 31.6 years, 411 PISA pointsCosta Rica: 34.1 years, 411 PISA pointsCyprus: 37.8 years, 411 PISA pointsCzechia: 42.7 years, 498 PISA pointsGermany: 45.1 years, 492 PISA pointsDenmark: 41.2 years, 494 PISA pointsDominican Republic: 27.7 years, 360 PISA pointsAlgeria: 28.2 years, 376 PISA pointsSpain: 44.9 years, 485 PISA pointsEstonia: 41.9 years, 526 PISA pointsFinland: 42.8 years, 511 PISA pointsFrance: 41.8 years, 487 PISA pointsUnited Kingdom: 39.8 years, 500 PISA pointsGeorgia: 36.8 years, 384 PISA pointsGreece: 45.7 years, 441 PISA pointsGuatemala: 22.6 years, 373 PISA pointsHong Kong SAR, China: 46.2 years, 520 PISA pointsCroatia: 44.8 years, 483 PISA pointsHungary: 43.3 years, 486 PISA pointsIndonesia: 29.8 years, 383 PISA pointsIreland: 38.4 years, 504 PISA pointsIceland: 35.8 years, 447 PISA pointsIsrael: 29.1 years, 465 PISA pointsItaly: 47.5 years, 477 PISA pointsJamaica: 31.7 years, 403 PISA pointsJordan: 24.3 years, 375 PISA pointsJapan: 49 years, 547 PISA pointsKazakhstan: 29.5 years, 423 PISA pointsCambodia: 25.8 years, 347 PISA pointsKorea, Rep.: 44.5 years, 528 PISA pointsLebanon: 28.3 years, 384 PISA pointsLithuania: 42.1 years, 484 PISA pointsLuxembourg: 38.9 years, 477 PISA pointsLatvia: 43.1 years, 494 PISA pointsMacao SAR, China: 38.3 years, 543 PISA pointsMorocco: 29.2 years, 365 PISA pointsMoldova: 37.8 years, 417 PISA pointsMexico: 28.9 years, 410 PISA pointsNorth Macedonia: 40.3 years, 380 PISA pointsMalta: 40.3 years, 466 PISA pointsMontenegro: 39.3 years, 403 PISA pointsMongolia: 26.8 years, 412 PISA pointsMalaysia: 30.1 years, 416 PISA pointsNetherlands: 41.4 years, 488 PISA pointsNorway: 39.5 years, 478 PISA pointsNew Zealand: 37.3 years, 504 PISA pointsPanama: 29.6 years, 388 PISA pointsPeru: 29.5 years, 408 PISA pointsPhilippines: 25.3 years, 356 PISA pointsPoland: 41.3 years, 499 PISA pointsPortugal: 46.2 years, 484 PISA pointsParaguay: 26.3 years, 368 PISA pointsWest Bank and Gaza: 19.8 years, 369 PISA pointsQatar: 33.2 years, 432 PISA pointsRomania: 42.6 years, 428 PISA pointsRussian Federation: 39.5 years, 478 PISA pointsSaudi Arabia: 29.2 years, 390 PISA pointsSingapore: 35.1 years, 561 PISA pointsEl Salvador: 27 years, 373 PISA pointsSerbia: 43.9 years, 447 PISA pointsSlovak Republic: 41.3 years, 462 PISA pointsSlovenia: 43.9 years, 500 PISA pointsSweden: 39.9 years, 494 PISA pointsThailand: 39.7 years, 409 PISA pointsTrinidad and Tobago: 36.7 years, 425 PISA pointsTunisia: 32.1 years, 386 PISA pointsTurkiye: 32.5 years, 476 PISA pointsUkraine: 42 years, 450 PISA pointsUruguay: 35.8 years, 435 PISA pointsUnited States: 38 years, 499 PISA pointsUzbekistan: 26.9 years, 355 PISA pointsViet Nam: 32.4 years, 472 PISA pointsKosovo: 31.4 years, 357 PISA pointsBGRBIHGTMHKGISRJPNKHMKORMACMKDPSESGP

best-fit line line after adjusting

Four ways to measure the link

MethodrpCountries
Standard (Pearson), not adjusted+0.7166.3e-1587
By rank (Spearman), not adjusted+0.6995.4e-1487
Standard (Pearson), adjusted for national income+0.4961.2e-687
By rank (Spearman), adjusted for national income+0.5417.6e-887

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 87 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: +0.220 (a minus sign means it grew).

How solid is it?

Leaving out one country at a time, r ranges from +0.464 (without SAU) to +0.532 (without SGP). 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: SGP (+0.035).

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 & Pacific15+0.64
Europe & Central Asia44+0.46
Latin America & Caribbean15+0.81

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 third29+0.38
Middle third29+0.52
Richest third29+0.67

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
Christians55+0.54
Muslims18-0.03

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
Spain14+0.74
United Kingdom14+0.45

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 = +0.496 after dropping 0 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 17years. So a link here can’t come from anything about a country that stays the same, such as its history, geography, institutions or culture.

Within countries over time, there is no link that is clearly more than chance (r = +0.048, comparing each country only with itself over the years, and each year only with the same year elsewhere). Whatever the cross-country picture shows, countries whose median age moved did not tend to see their pisa science move with it.

Across countries (adjusted)+0.496for comparison
Within countries-0.141each country vs itself
…and vs the same year elsewhere+0.048q = 0.758 · 56 countries
Year-on-year changes—q = —
Read with care.
  • Almost all of this indicator's variation is between countries, not within them, so the within-country estimate rests on a small part of the data.

330 country-years (one country in one year), 56 countries, 2006–2022, about 6 years each on average. Share of the variation that happens within countries over time: 5% for Median age, 8% for PISA science. 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

0.10−0.1-50+10years PISA science trails Median age →lag -5: r = 0.080 (n = 260)lag -4: r = 0.036 (n = 260)lag -3: r = 0.020 (n = 260)lag -2: r = 0.019 (n = 260)lag -1: r = 0.078 (n = 330)lag +0: r = 0.048 (n = 330)lag +1: r = 0.026 (n = 330)lag +2: r = 0.009 (n = 330)lag +3: r = -0.006 (n = 330)lag +4: r = -0.008 (n = 330)lag +5: r = -0.007 (n = 330)lag +6: r = -0.016 (n = 330)lag +7: r = -0.025 (n = 330)lag +8: r = -0.033 (n = 330)lag +9: r = -0.050 (n = 330)lag +10: r = -0.060 (n = 330)

Same year (lag 0): +0.048. 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 -5), 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


years
PISA points		Years
Japan JPN495472023, 2022
Italy ITA47.54772023, 2022
Portugal PRT46.24842023, 2022
Hong Kong SAR, China HKG46.25202023, 2022
Greece GRC45.74412023, 2022
Germany DEU45.14922023, 2022
Bosnia and Herzegovina BIH44.93982023, 2018
Spain ESP44.94852023, 2022
Croatia HRV44.84832023, 2022
Korea, Rep. KOR44.55282023, 2022
Bulgaria BGR44.34212023, 2022
Slovenia SVN43.95002023, 2022
Serbia SRB43.94472023, 2022
Hungary HUN43.34862023, 2022
Austria AUT43.14912023, 2022

United Nations, Department of Economic and Social Affairs, Population Division: World Population Prospects 2024 and Estimates and Projections of Women of Reproductive Age Who Are Married or in a Union
OECD databases as named on each indicator: PISA, Social Expenditure Database (SOCX), Income Distribution Database, Development Assistance Committee statistics, Family Database, Government at a Glance, Corporate Tax Statistics, employment and environment statistics

Sources

Median age

Median age of the population

United Nations Department of Economic and Social Affairs, Population Division · via Our World in Data · CC BY 3.0 IGO · updated biennial

The age that splits a population in half: half are older and half are younger. The shares aged under 15 and over 65 are already on the site. All three are treated as measuring the same thing. They are readings of the same age pyramid, so they are bound to match, and their agreement is not a finding. No "better" direction is set.

PISA science

PISA mean science score

OECD · via Our World in Data · CC BY 4.0 (OECD terms and conditions) · updated annual, except the snapshots noted per indicator

How this was computed

Data used: most recent value in 2010-2025; values come from 2015–2023. 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 5 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 Median age and PISA science

This page shows that two measures go together. It does not show that Median age changes PISA science, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.

More links with Median age or PISA science