placestats

Basic water access vs. Undernourishment

Fades after adjusting for income

Across 162 countries, Basic water access and Undernourishment rise and fall together at r = -0.70 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to -0.30, which could easily be chance (q = 0.17, 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. Caution: direction is not consistent across regions.

Comparing countries across the middle half of basic water access, 86.2% to 99.6% of population, undernourishment is better by 7% of population at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 3.5% of population.

Link before adjusting (r)-0.703p = 1.7e-25 · 162 countries
After adjusting for national income-0.303p = 9.1e-5 · likely range [-0.44, -0.16]
p, allowing for regions0.045standard error 0.120 · 7 regions
Check for luck (q)0.171across 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.

Basic water access · % of populationlink with income +0.85 · proxy
Undernourishment · % of populationlink with income -0.83 · proxy

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

Basic water access · % of population →Undernourishment · % of population →35.7%100%2.5%54.2%Afghanistan: 80.8% of population, 28.1% of populationAngola: 68% of population, 22.5% of populationAlbania: 95.1% of population, 5.4% of populationUnited Arab Emirates: 100% of population, 2.5% of populationArgentina: 99% of population, 3.4% of populationArmenia: 99.9% of population, 2.5% of populationAustralia: 100% of population, 2.5% of populationAustria: 100% of population, 2.5% of populationAzerbaijan: 97.7% of population, 2.5% of populationBelgium: 100% of population, 2.5% of populationBenin: 69.6% of population, 14.3% of populationBurkina Faso: 50% of population, 13.1% of populationBangladesh: 98.8% of population, 10.4% of populationBulgaria: 99.2% of population, 2.5% of populationBosnia and Herzegovina: 96.1% of population, 2.5% of populationBelarus: 99.9% of population, 2.5% of populationBelize: 94.8% of population, 7% of populationBolivia: 93.4% of population, 21.8% of populationBrazil: 100% of population, 2.5% of populationBarbados: 99.2% of population, 4.4% of populationBotswana: 91.8% of population, 24% of populationCentral African Republic: 36.5% of population, 29.8% of populationCanada: 98.3% of population, 2.5% of populationSwitzerland: 100% of population, 2.5% of populationChile: 99.1% of population, 2.5% of populationChina: 96.1% of population, 2.5% of populationCote d'Ivoire: 77.2% of population, 11.1% of populationCameroon: 71.4% of population, 4.8% of populationCongo, Dem. Rep.: 35.7% of population, 38.5% of populationCongo, Rep.: 73.5% of population, 26.4% of populationColombia: 97.1% of population, 3.9% of populationComoros: 85.1% of population, 15.4% of populationCabo Verde: 92.3% of population, 13.5% of populationCosta Rica: 99.8% of population, 2.5% of populationCyprus: 99.7% of population, 2.5% of populationCzechia: 98.7% of population, 2.5% of populationGermany: 100% of population, 2.5% of populationDjibouti: 79.7% of population, 12.9% of populationDominica: 97% of population, 3.6% of populationDenmark: 100% of population, 2.5% of populationDominican Republic: 97.5% of population, 3.6% of populationAlgeria: 92.4% of population, 2.5% of populationEcuador: 92.1% of population, 12.1% of populationEgypt, Arab Rep.: 97.3% of population, 9.4% of populationSpain: 99.9% of population, 2.5% of populationEstonia: 100% of population, 2.5% of populationEthiopia: 55.6% of population, 19.7% of populationFinland: 100% of population, 2.5% of populationFiji: 95.6% of population, 6.8% of populationFrance: 100% of population, 2.5% of populationGabon: 88.6% of population, 25.3% of populationUnited Kingdom: 100% of population, 2.5% of populationGeorgia: 97.3% of population, 2.5% of populationGhana: 89.9% of population, 6.3% of populationGuinea: 74.2% of population, 11.4% of populationGambia, The: 87.1% of population, 16.8% of populationGuinea-Bissau: 61.8% of population, 22.1% of populationGreece: 100% of population, 2.5% of populationGuatemala: 93.2% of population, 11.8% of populationGuyana: 95.6% of population, 2.5% of populationHong Kong SAR, China: 100% of population, 3.1% of populationHonduras: 95.7% of population, 14.8% of populationCroatia: 99.9% of population, 2.5% of populationHaiti: 73.3% of population, 54.2% of populationHungary: 100% of population, 2.5% of populationIndonesia: 89% of population, 6.3% of populationIndia: 95.7% of population, 12% of populationIreland: 97.1% of population, 2.5% of populationIran, Islamic Rep.: 97.9% of population, 6.8% of populationIraq: 98.4% of population, 14.9% of populationIceland: 100% of population, 2.5% of populationIsrael: 100% of population, 2.5% of populationItaly: 99.9% of population, 2.5% of populationJamaica: 87.6% of population, 7.7% of populationJordan: 99.3% of population, 14.3% of populationKazakhstan: 97.8% of population, 2.5% of populationKenya: 65.6% of population, 36.8% of populationKyrgyz Republic: 94.9% of population, 5.1% of populationCambodia: 82.8% of population, 5.2% of populationKiribati: 79.1% of population, 4.1% of populationKorea, Rep.: 100% of population, 2.5% of populationKuwait: 100% of population, 2.5% of populationLebanon: 92.6% of population, 8.7% of populationLiberia: 78.8% of population, 35.5% of populationLibya: 96.4% of population, 16.5% of populationSri Lanka: 90.2% of population, 7.4% of populationLithuania: 99.9% of population, 2.5% of populationLuxembourg: 100% of population, 2.5% of populationLatvia: 98.8% of population, 2.5% of populationMacao SAR, China: 100% of population, 11.2% of populationMorocco: 92.2% of population, 7% of populationMoldova: 92.7% of population, 2.5% of populationMadagascar: 55.3% of population, 39.5% of populationMexico: 99.5% of population, 2.7% of populationNorth Macedonia: 98.2% of population, 2.5% of populationMali: 86.4% of population, 12.3% of populationMalta: 100% of population, 2.5% of populationMyanmar: 85.7% of population, 5.4% of populationMontenegro: 99.3% of population, 2.5% of populationMongolia: 86.1% of population, 2.5% of populationMozambique: 66.6% of population, 21.8% of populationMauritania: 77.3% of population, 8.7% of populationMauritius: 99.9% of population, 8.7% of populationMalawi: 73.1% of population, 21.4% of populationMalaysia: 97.9% of population, 2.5% of populationNamibia: 86.5% of population, 18.1% of populationNiger: 53.4% of population, 12.9% of populationNigeria: 82.2% of population, 19.9% of populationNetherlands: 100% of population, 2.5% of populationNorway: 100% of population, 2.5% of populationNepal: 93.6% of population, 5.3% of populationNew Zealand: 100% of population, 2.5% of populationOman: 92.7% of population, 5.9% of populationPakistan: 90.7% of population, 16.5% of populationPanama: 95.3% of population, 5.7% of populationPeru: 95.6% of population, 6.9% of populationPhilippines: 95.9% of population, 3% of populationPapua New Guinea: 53.3% of population, 28.7% of populationPoland: 90.1% of population, 2.5% of populationPortugal: 99.3% of population, 2.5% of populationParaguay: 99.6% of population, 5.2% of populationRomania: 100% of population, 2.5% of populationRussian Federation: 96.9% of population, 2.5% of populationRwanda: 61.4% of population, 24.4% of populationSaudi Arabia: 99% of population, 2.5% of populationSudan: 64.9% of population, 11% of populationSenegal: 88% of population, 5.1% of populationSolomon Islands: 71.6% of population, 20% of populationSierra Leone: 68.1% of population, 24.1% of populationEl Salvador: 91.6% of population, 6.7% of populationSomalia, Fed. Rep.: 75.3% of population, 53.2% of populationSerbia: 95.4% of population, 2.5% of populationSao Tome and Principe: 78% of population, 17.4% of populationSuriname: 98% of population, 9.7% of populationSlovak Republic: 99.8% of population, 3.1% of populationSlovenia: 99.6% of population, 2.5% of populationSweden: 99.8% of population, 2.5% of populationEswatini: 80.4% of population, 14.7% of populationSeychelles: 97.7% of population, 2.5% of populationSyrian Arab Republic: 94.1% of population, 39% of populationChad: 52.2% of population, 32% of populationTogo: 64.8% of population, 9.1% of populationThailand: 100% of population, 4.6% of populationTajikistan: 89.2% of population, 8.4% of populationTurkmenistan: 99.9% of population, 4.3% of populationTimor-Leste: 87.3% of population, 18.7% of populationTrinidad and Tobago: 99.3% of population, 11.2% of populationTunisia: 96.7% of population, 3% of populationTurkiye: 96% of population, 2.5% of populationTanzania: 64.6% of population, 20.2% of populationUganda: 63% of population, 22% of populationUkraine: 93.5% of population, 6.9% of populationUruguay: 99.6% of population, 2.5% of populationUnited States: 100% of population, 2.5% of populationUzbekistan: 97.3% of population, 2.5% of populationSt. Vincent and the Grenadines: 97.7% of population, 6.1% of populationViet Nam: 98.8% of population, 5.3% of populationVanuatu: 87.1% of population, 7.2% of populationSamoa: 99.4% of population, 3.6% of populationSouth Africa: 90.2% of population, 10% of populationZambia: 73.4% of population, 37.2% of populationZimbabwe: 67.2% of population, 19.7% of populationBFACAFCODHTINERNLDNORNZLSOMSYR

best-fit line line after adjusting

Four ways to measure the link

MethodrpCountries
Standard (Pearson), not adjusted-0.7031.7e-25162
By rank (Spearman), not adjusted-0.7697.3e-33162
Standard (Pearson), adjusted for national income-0.3039.1e-5162
By rank (Spearman), adjusted for national income-0.1640.038162

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 162 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: +0.400 (a minus sign means it grew).

How solid is it?

Leaving out one country at a time, r ranges from -0.353 (without SYR) to -0.271 (without COD). 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: SYR (-0.050).

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.

nr
East Asia & Pacific21-0.70
Europe & Central Asia48-0.36
Latin America & Caribbean25-0.70
Middle East, North Africa, Afghanistan & Pakistan19+0.26
Sub-Saharan Africa43-0.16

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 third54-0.18
Middle third54-0.25
Richest third54-0.13

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
Christians99-0.42
Muslims44+0.09

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
France24+0.08
Never a European colony20-0.33
Spain17-0.36
United Kingdom48-0.34

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 = -0.366 after dropping 20 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 23years. 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 also shows up within countries over time (r = -0.339). It holds even when looking only at changes from one year to the next (r = -0.187). This is the strongest kind of evidence available here: it holds when each country is compared only with itself, and it is not just a product of shared trends.

Across countries (adjusted)-0.303for comparison
Within countries-0.452each country vs itself
…and vs the same year elsewhere-0.339q = 0.000 · 167 countries
Year-on-year changes-0.187q = 8.0e-5
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.

3,765 country-years (one country in one year), 167 countries, 2001–2023, about 23 years each on average. Share of the variation that happens within countries over time: 6% for Basic water access, 13% for Undernourishment. 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

0.50−0.5-100+10years Undernourishment trails Basic water access →lag -10: r = -0.415 (n = 2,298)lag -9: r = -0.406 (n = 2,463)lag -8: r = -0.393 (n = 2,628)lag -7: r = -0.384 (n = 2,798)lag -6: r = -0.378 (n = 2,963)lag -5: r = -0.374 (n = 3,128)lag -4: r = -0.369 (n = 3,291)lag -3: r = -0.363 (n = 3,451)lag -2: r = -0.354 (n = 3,610)lag -1: r = -0.344 (n = 3,769)lag +0: r = -0.339 (n = 3,765)lag +1: r = -0.336 (n = 3,761)lag +2: r = -0.316 (n = 3,598)lag +3: r = -0.291 (n = 3,430)lag +4: r = -0.263 (n = 3,267)lag +5: r = -0.228 (n = 3,104)lag +6: r = -0.189 (n = 2,940)lag +7: r = -0.150 (n = 2,776)lag +8: r = -0.111 (n = 2,611)lag +9: r = -0.076 (n = 2,446)lag +10: r = -0.047 (n = 2,281)

Same year (lag 0): -0.339. 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


% of population
% of population		Years
Thailand THA100%4.6%2024, 2023
New Zealand NZL100%2.5%2024, 2023
Norway NOR100%2.5%2024, 2023
Netherlands NLD100%2.5%2024, 2023
Malta MLT100%2.5%2024, 2023
Macao SAR, China MAC100%11.2%2024, 2023
Luxembourg LUX100%2.5%2024, 2023
Kuwait KWT100%2.5%2024, 2023
Korea, Rep. KOR100%2.5%2024, 2023
Iceland ISL100%2.5%2024, 2023
Hungary HUN100%2.5%2024, 2023
Hong Kong SAR, China HKG100%3.1%2024, 2023
Greece GRC100%2.5%2024, 2023
Germany DEU100%2.5%2024, 2023
Belgium BEL100%2.5%2024, 2023

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

Sources

Basic water access

People using at least basic drinking water services (% of population)

World Bank · CC BY 4.0 · updated quarterly

Undernourishment

Prevalence of undernourishment (% of population)

Food and Agriculture Organization · CC BY 4.0 · updated quarterly

Estimated from the food supply and how it is shared out, not by asking anyone. It is the FAO's model of how many people get less food energy than they need. The survey-based food insecurity measure below is treated as measuring the same thing. So their pair reads as two tools agreeing, not as a finding.

How this was computed

Data used: most recent value in 2010-2025; values come from 2016–2024. 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 Basic water access and Undernourishment

This page shows that two measures go together. It does not show that Basic water access changes Undernourishment, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.

More links with Basic water access or Undernourishment