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Pupil-teacher ratio vs. Tobacco use

Holds up after adjusting for income

Across 154 countries, Pupil-teacher ratio and Tobacco use rise and fall together at r = -0.38 (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 = 0.037, allowing for the many pairs tested).

Comparing countries across the middle half of tobacco use, 11.3% to 26.6% of adults, pupil-teacher ratio is better by 6.88 pupils per teacher at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 4.15 pupils per teacher.

Link before adjusting (r)-0.381p = 1.1e-6 · 154 countries
After adjusting for national income-0.380p = 1.3e-6 · likely range [-0.51, -0.24]
p, allowing for regions0.007standard error 0.095 · 7 regions
Check for luck (q)0.037across 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.

Pupil-teacher ratio · pupils per teacherlink with income -0.83 · proxy
Tobacco use · % of adultslink with income +0.24 · independent

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

Every country as a dot

Pupil-teacher ratio · pupils per teacher →Tobacco use · % of adults →8.359.53.1%48.8%Afghanistan: 48.8 pupils per teacher, 22.1% of adultsAlbania: 17.6 pupils per teacher, 21.4% of adultsAndorra: 10.5 pupils per teacher, 35.5% of adultsUnited Arab Emirates: 24.5 pupils per teacher, 9% of adultsArmenia: 15.4 pupils per teacher, 26.2% of adultsAustria: 10 pupils per teacher, 23.8% of adultsAzerbaijan: 15.4 pupils per teacher, 18.7% of adultsBurundi: 42.5 pupils per teacher, 10.1% of adultsBelgium: 11.3 pupils per teacher, 23.5% of adultsBenin: 39.2 pupils per teacher, 7.4% of adultsBurkina Faso: 39.7 pupils per teacher, 11.6% of adultsBangladesh: 30.1 pupils per teacher, 32% of adultsBulgaria: 15.2 pupils per teacher, 38.7% of adultsBahrain: 11.9 pupils per teacher, 15.4% of adultsBahamas, The: 19.4 pupils per teacher, 17.3% of adultsBosnia and Herzegovina: 16.9 pupils per teacher, 37.1% of adultsBelarus: 19.2 pupils per teacher, 29.2% of adultsBelize: 19.8 pupils per teacher, 8.5% of adultsBolivia: 17.8 pupils per teacher, 12.3% of adultsBrazil: 20.2 pupils per teacher, 11.9% of adultsBrunei Darussalam: 9.9 pupils per teacher, 14.5% of adultsBhutan: 34.7 pupils per teacher, 19.6% of adultsBotswana: 23.7 pupils per teacher, 18% of adultsSwitzerland: 9.93 pupils per teacher, 23.1% of adultsChile: 17.8 pupils per teacher, 26.7% of adultsChina: 16.4 pupils per teacher, 22.8% of adultsCote d'Ivoire: 41.8 pupils per teacher, 7.3% of adultsCameroon: 44.8 pupils per teacher, 5.7% of adultsCongo, Dem. Rep.: 33.2 pupils per teacher, 12.3% of adultsCongo, Rep.: 44.4 pupils per teacher, 16.2% of adultsColombia: 23.3 pupils per teacher, 8% of adultsComoros: 28.1 pupils per teacher, 8.9% of adultsCabo Verde: 21.1 pupils per teacher, 10.4% of adultsCosta Rica: 12.2 pupils per teacher, 7.9% of adultsCyprus: 12 pupils per teacher, 32.5% of adultsCzechia: 18.9 pupils per teacher, 28.4% of adultsGermany: 12.3 pupils per teacher, 22% of adultsDenmark: 10.7 pupils per teacher, 15.7% of adultsAlgeria: 24.3 pupils per teacher, 22.4% of adultsEcuador: 24.3 pupils per teacher, 10.1% of adultsEgypt, Arab Rep.: 23.7 pupils per teacher, 25% of adultsSpain: 13.1 pupils per teacher, 27.6% of adultsEstonia: 11.3 pupils per teacher, 26.1% of adultsEthiopia: 55.1 pupils per teacher, 5.2% of adultsFinland: 13.7 pupils per teacher, 21.4% of adultsFiji: 28 pupils per teacher, 25.8% of adultsFrance: 18.2 pupils per teacher, 33.6% of adultsGabon: 24.5 pupils per teacher, 13.3% of adultsUnited Kingdom: 15.1 pupils per teacher, 12.8% of adultsGeorgia: 8.98 pupils per teacher, 33% of adultsGhana: 27 pupils per teacher, 3.3% of adultsGambia, The: 36.1 pupils per teacher, 11.1% of adultsGuinea-Bissau: 51.9 pupils per teacher, 8.2% of adultsGreece: 9.38 pupils per teacher, 30.2% of adultsGuatemala: 20.3 pupils per teacher, 11.2% of adultsGuyana: 23.2 pupils per teacher, 11.7% of adultsHonduras: 25.6 pupils per teacher, 12.1% of adultsCroatia: 13.5 pupils per teacher, 34.4% of adultsHungary: 10.8 pupils per teacher, 30.8% of adultsIndonesia: 17 pupils per teacher, 31% of adultsIndia: 32.7 pupils per teacher, 22.6% of adultsIreland: 16.1 pupils per teacher, 18.2% of adultsIran, Islamic Rep.: 28.5 pupils per teacher, 11.9% of adultsIceland: 10.1 pupils per teacher, 9.2% of adultsIsrael: 12.1 pupils per teacher, 21.2% of adultsItaly: 11.5 pupils per teacher, 22.4% of adultsJamaica: 24.8 pupils per teacher, 11.5% of adultsJordan: 18.5 pupils per teacher, 34.1% of adultsJapan: 15.7 pupils per teacher, 17.5% of adultsKazakhstan: 17.2 pupils per teacher, 21.1% of adultsKenya: 30.7 pupils per teacher, 9.6% of adultsKyrgyz Republic: 25 pupils per teacher, 22.2% of adultsCambodia: 41.7 pupils per teacher, 18.6% of adultsKiribati: 25.5 pupils per teacher, 37.7% of adultsKorea, Rep.: 16.3 pupils per teacher, 18.6% of adultsKuwait: 8.88 pupils per teacher, 19.4% of adultsLao PDR: 22.3 pupils per teacher, 25.4% of adultsLebanon: 12.5 pupils per teacher, 46.9% of adultsLiberia: 22.3 pupils per teacher, 5.2% of adultsSt. Lucia: 14.7 pupils per teacher, 13.9% of adultsSri Lanka: 21.7 pupils per teacher, 20.7% of adultsLesotho: 32.9 pupils per teacher, 28% of adultsLithuania: 13.5 pupils per teacher, 31.4% of adultsLuxembourg: 8.3 pupils per teacher, 24.5% of adultsLatvia: 11.5 pupils per teacher, 34.6% of adultsMorocco: 26.8 pupils per teacher, 12.5% of adultsMoldova: 17.9 pupils per teacher, 28.8% of adultsMadagascar: 39.8 pupils per teacher, 25.6% of adultsMaldives: 10.2 pupils per teacher, 25.5% of adultsMexico: 26.6 pupils per teacher, 15.7% of adultsNorth Macedonia: 14.9 pupils per teacher, 39.6% of adultsMali: 37.8 pupils per teacher, 7.4% of adultsMalta: 12.9 pupils per teacher, 24.6% of adultsMyanmar: 24.4 pupils per teacher, 43.4% of adultsMongolia: 30.4 pupils per teacher, 29.5% of adultsMozambique: 55.3 pupils per teacher, 10.5% of adultsMauritania: 34.3 pupils per teacher, 9.9% of adultsMauritius: 16.2 pupils per teacher, 17.7% of adultsMalawi: 58.7 pupils per teacher, 8.9% of adultsMalaysia: 11.7 pupils per teacher, 16.9% of adultsNiger: 36.3 pupils per teacher, 7.4% of adultsNigeria: 37.6 pupils per teacher, 3.1% of adultsNetherlands: 11.8 pupils per teacher, 20.5% of adultsNorway: 8.59 pupils per teacher, 12.9% of adultsNepal: 19.7 pupils per teacher, 28.7% of adultsNaoero: 40.2 pupils per teacher, 34.8% of adultsNew Zealand: 14.9 pupils per teacher, 9.3% of adultsOman: 9.67 pupils per teacher, 8.5% of adultsPakistan: 44.1 pupils per teacher, 17.9% of adultsPanama: 22 pupils per teacher, 4.8% of adultsPeru: 17.4 pupils per teacher, 12.4% of adultsPhilippines: 29.1 pupils per teacher, 19.9% of adultsPapua New Guinea: 35.5 pupils per teacher, 39.3% of adultsPoland: 10.2 pupils per teacher, 21.7% of adultsPortugal: 12.4 pupils per teacher, 28.6% of adultsParaguay: 24.2 pupils per teacher, 6.4% of adultsWest Bank and Gaza: 24.5 pupils per teacher, 35.5% of adultsQatar: 12.2 pupils per teacher, 12.5% of adultsRomania: 19.3 pupils per teacher, 29.7% of adultsRussian Federation: 21.3 pupils per teacher, 27% of adultsRwanda: 59.5 pupils per teacher, 10.1% of adultsSaudi Arabia: 13.8 pupils per teacher, 14.7% of adultsSenegal: 36.3 pupils per teacher, 5.4% of adultsSingapore: 14.7 pupils per teacher, 13.8% of adultsSolomon Islands: 25.4 pupils per teacher, 38.4% of adultsSierra Leone: 27.5 pupils per teacher, 11.3% of adultsEl Salvador: 26.9 pupils per teacher, 8.2% of adultsSerbia: 14.3 pupils per teacher, 39.7% of adultsSao Tome and Principe: 31.2 pupils per teacher, 8.3% of adultsSlovak Republic: 15.5 pupils per teacher, 29.5% of adultsSlovenia: 13.8 pupils per teacher, 20.9% of adultsSweden: 12.2 pupils per teacher, 20.3% of adultsEswatini: 26.6 pupils per teacher, 11.5% of adultsSeychelles: 14.5 pupils per teacher, 17.3% of adultsChad: 56.9 pupils per teacher, 7.4% of adultsTogo: 40.1 pupils per teacher, 5.8% of adultsThailand: 16.6 pupils per teacher, 17.8% of adultsTimor-Leste: 26.9 pupils per teacher, 48.8% of adultsTonga: 21.6 pupils per teacher, 32.1% of adultsTunisia: 16.9 pupils per teacher, 24.4% of adultsTurkiye: 17 pupils per teacher, 31.1% of adultsTuvalu: 15.6 pupils per teacher, 33.4% of adultsTanzania: 50.6 pupils per teacher, 7.7% of adultsUganda: 42.7 pupils per teacher, 7.5% of adultsUkraine: 13 pupils per teacher, 23.7% of adultsUruguay: 11 pupils per teacher, 19.3% of adultsUnited States: 14.2 pupils per teacher, 15.8% of adultsUzbekistan: 21.5 pupils per teacher, 16.3% of adultsViet Nam: 20.3 pupils per teacher, 21.1% of adultsVanuatu: 26.6 pupils per teacher, 24.9% of adultsSamoa: 30.2 pupils per teacher, 23.1% of adultsSouth Africa: 30.3 pupils per teacher, 23.7% of adultsZambia: 42.1 pupils per teacher, 14.3% of adultsZimbabwe: 36.4 pupils per teacher, 11% of adultsCRIETHISLLBNMKDMWINRUOMNPNGSRBTCDTLS

best-fit line line after adjusting

Four ways to measure the link

MethodrpCountries
Standard (Pearson), not adjusted-0.3811.1e-6154
By rank (Spearman), not adjusted-0.3877.4e-7154
Standard (Pearson), adjusted for national income-0.3801.3e-6154
By rank (Spearman), adjusted for national income-0.3263.9e-5154

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 154 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: +0.001 (a minus sign means it grew).

How solid is it?

Leaving out one country at a time, r ranges from -0.412 (without LBR) to -0.357 (without LBN). 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: LBR (-0.032).

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 & Pacific25-0.06
Europe & Central Asia46-0.07
Latin America & Caribbean19-0.29
Middle East, North Africa, Afghanistan & Pakistan18-0.67
Sub-Saharan Africa39-0.19

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 third52-0.49
Middle third51-0.15
Richest third51-0.21

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
Christians91-0.36
Muslims40-0.52

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
France20-0.57
Never a European colony19-0.14
Spain15-0.11
United Kingdom49-0.42

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 = -0.352 after dropping 5 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 16years. 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 = +0.068, 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 pupil-teacher ratio moved did not tend to see their tobacco use move with it.

Across countries (adjusted)-0.380for comparison
Within countries+0.474each country vs itself
…and vs the same year elsewhere+0.068q = 0.679 · 70 countries
Year-on-year changes—q = —
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.
  • Much of the within-country association disappears once shared global year effects are removed, which points to a common worldwide trend rather than a country-level relationship.

350 country-years (one country in one year), 70 countries, 2000–2015, about 5 years each on average. Share of the variation that happens within countries over time: 11% for Pupil-teacher ratio, 5% for Tobacco use. 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

0.20−0.2-30+10years Tobacco use trails Pupil-teacher ratio →lag -3: r = 0.058 (n = 200)lag -2: r = 0.134 (n = 350)lag -1: r = -0.062 (n = 385)lag +0: r = 0.068 (n = 350)lag +1: r = 0.038 (n = 396)lag +2: r = -0.010 (n = 421)lag +3: r = -0.019 (n = 495)lag +4: r = -0.038 (n = 609)lag +5: r = 0.034 (n = 726)lag +6: r = 0.039 (n = 929)lag +7: r = 0.020 (n = 926)lag +8: r = -0.015 (n = 907)lag +9: r = -0.072 (n = 888)lag +10: r = -0.079 (n = 874)

Same year (lag 0): +0.068. 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 (+0.13 at lag -2) is higher than the same-year one by 0.07. That gap is not a finding. It is the largest of 14 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


pupils per teacher
% of adults		Years
Rwanda RWA59.510.1%2018, 2024
Malawi MWI58.78.9%2018, 2024
Chad TCD56.97.4%2016, 2024
Mozambique MOZ55.310.5%2018, 2024
Ethiopia ETH55.15.2%2011, 2024
Guinea-Bissau GNB51.98.2%2010, 2024
Tanzania TZA50.67.7%2018, 2024
Afghanistan AFG48.822.1%2018, 2024
Cameroon CMR44.85.7%2018, 2024
Congo, Rep. COG44.416.2%2012, 2024
Pakistan PAK44.117.9%2018, 2024
Uganda UGA42.77.5%2017, 2024
Burundi BDI42.510.1%2018, 2024
Zambia ZMB42.114.3%2017, 2024
Cote d'Ivoire CIV41.87.3%2018, 2024

World Bank, World Development Indicators
World Bank, World Development Indicators

Sources

Pupil-teacher ratio

Pupil-teacher ratio, primary

UNESCO Institute for Statistics · CC BY 4.0 · updated quarterly

The World Bank's copy stops at 2019.

Tobacco use

Prevalence of current tobacco use (% of adults, age-standardised)

World Health Organization · CC BY 4.0 · updated quarterly

Published every other year.

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 12,497 pairs at once, using the Benjamini–Hochberg method. Underlying data last updated DYB 2024. How the country data works · explore Pupil-teacher ratio and Tobacco use

This page shows that two measures go together. It does not show that Pupil-teacher ratio changes Tobacco use, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.

More links with Pupil-teacher ratio or Tobacco use