What the HDI measures, in one sentence
The Human Development Index is published by the United Nations Development Programme (UNDP). According to the index page, it summarises three dimensions: health, education and standard of living.
- Health
- Life expectancy at birth.
- Education
- Mean years of schooling for adults aged 25 and over, and expected years of schooling for children of school-entering age.
- Standard of living
- Gross national income (GNI) per capita, in 2021 purchasing-power-parity dollars, used through the logarithm.
The final value falls between 0 and 1. UNDP describes the HDI as “the geometric mean of normalized indices for each of the three dimensions”.
How the value is calculated, with Brazil as the example
Each dimension becomes an index between 0 and 1 by comparing the country’s value with a floor and a ceiling. UNDP’s calculation workbook uses 20 and 85 years for life expectancy, 0 and 18 for expected years of schooling, 0 and 15 for mean years, and 100 and 75,000 dollars for income.
I_saude = (EV - 20) / (85 - 20)
I_educ = ( AEE/18 + AME/15 ) / 2
I_renda = ( ln(RNB) - ln(100) ) / ( ln(75000) - ln(100) )
IDH = ( I_saude x I_educ x I_renda ) ^ (1/3)- EV
- Life expectancy at birth, in years
- AEE
- Expected years of schooling
- AME
- Mean years of schooling
- RNB
- Gross national income per capita, in 2021 PPP US$
Worked example with Brazil, using UNDP’s 2023 data: life expectancy 75.848 years, expected schooling 15.79, mean schooling 8.43 and income of 18,011 dollars.
- Health(75.848 - 20) / 65 = 0.859.
- Education(15.79/18 + 8.43/15) / 2 = (0.877 + 0.562) / 2 = 0.720.
- Income(ln 18,011 - ln 100) / (ln 75,000 - ln 100) = 0.785.
- Geometric mean(0.859 x 0.720 x 0.785) to the power 1/3 = 0.786, the value UNDP publishes.
Why a geometric mean? Because it punishes imbalance: a country cannot offset weak education with income alone. And why the logarithm on income? Because each extra dollar weighs less for someone already wealthy.
See the effect on Brazil. Doubling income lifts the HDI to about 0.819, and one more year of life expectancy lifts it to about 0.790. These numbers are my own calculations on the formula above, not UNDP projections.
The 2023 ranking in ten countries
The ranking runs from 1 to 193. The values below come from the Human Development Report 2025 time-series file, downloaded on 2 November 2026, and were rounded. Norway and Switzerland tie for 2nd.
| Rank | Country | HDI | Life expectancy | Expected / mean years of schooling | Income per capita (2021 PPP US$) |
|---|---|---|---|---|---|
| 1 | Iceland | 0.972 | 82.7 | 18.9 / 13.9 | 69,117 |
| 2 | Norway | 0.970 | 83.3 | 18.8 / 13.1 | 112,710 |
| 2 | Switzerland | 0.970 | 84.0 | 16.7 / 13.9 | 81,949 |
| 4 | Denmark | 0.962 | 81.9 | 18.7 / 13.0 | 76,008 |
| 7 | Australia | 0.958 | 83.9 | 20.7 / 12.9 | 58,277 |
| 23 | Japan | 0.925 | 84.7 | 15.5 / 12.7 | 47,775 |
| 40 | Portugal | 0.890 | 82.4 | 17.5 / 9.7 | 41,064 |
| 84 | Brazil | 0.786 | 75.8 | 15.8 / 8.4 | 18,011 |
| 130 | India | 0.685 | 72.0 | 13.0 / 6.9 | 9,047 |
| 188 | Niger | 0.419 | 61.2 | 8.3 / 1.4 | 1,590 |
Look at Norway and Switzerland: identical HDI, different profiles. Norway has much higher income; Switzerland has longer life expectancy. The single number hides distinct combinations.
What the HDI does not measure
The HDI is a national average. It does not say how income is distributed, how much carbon the country emits, whether you will be welcome, whether you speak the language or whether you can get a visa.
UNDP itself publishes two adjustments. The IHDI discounts inequality within each dimension; the PHDI accounts for planetary pressure, with indices for CO2 emissions and material footprint.
| Country | HDI | IHDI | PHDI |
|---|---|---|---|
| Norway | 0.970 | 0.909 | 0.723 |
| United States | 0.938 | 0.832 | 0.686 |
| Portugal | 0.890 | 0.795 | 0.797 |
| United Arab Emirates | 0.940 | 0.866 | 0.585 |
| Qatar | 0.886 | no data | 0.276 |
| Brazil | 0.786 | 0.594 | 0.702 |
The reading is direct. In Brazil, the gap between the HDI (0.786) and the IHDI (0.594) is the largest in the table and points to high inequality. In Qatar, the PHDI of 0.276 reflects the environmental footprint, despite an HDI of 0.886.
How to use the HDI to choose where to live
- Filter by HDIUse the ranking to discard countries whose basics (health, schooling, income) do not meet the minimum you need.
- Look at the componentsTwo countries with the same HDI can differ in income and longevity. Pick the component that weighs most for you.
- Check the adjustmentsCompare HDI, IHDI and PHDI to see inequality and environmental pressure.
- Add what the index cannot seeLanguage, climate, cost of living, support network, visa and career decide the day to day. The which country should you live in quiz helps you rank those preferences.
To read rankings critically, it also helps to understand why correlation is not causation and how the normal distribution works.
Frequently asked questions
Which country has the highest HDI?
Where does Brazil rank on the HDI?
Does the HDI measure happiness or quality of life?
Why does the HDI use a geometric mean?
Can I reuse UNDP’s data?
The HDI is a good filter, not a verdict. It summarises health, education and income in a geometric mean, and so it hides inequality, environmental footprint and everything that depends on your lifestyle. Start from the ranking, open the components, and then compare what the index cannot see.