The HDI has been used by the UN since 1990, and measures:
These combine to give a score from 1 (best) to 0 (poor).
The UK, USA and Australia are all 0.9 and over. China, Saudi Arabia and Peru are 0.5 - 0.75. Sub-Saharan Africa and many other countries are under 0.25.
The map below shows world HDI rankings.
HDI gives a more accurate picture of a country’s situation than GNI. Countries with high GNI, such as oil rich Gulf states might not necessarily have high HDI scores, due to inequalities within these countries.
The map below shows countries by gross national income.
Both countries have a similar per capita GDP. However, life expectancy and literacy are considerably higher in Vietnam than they are in Pakistan. Vietnam has a much higher HDI value even though it has a similar per capita GDP.
Saudi Arabia has a per capita GDP comparable to that of Croatia. However, in Saudi Arabia there is greater inequality between men and women when considering access to education and political power.
So, although they are equal on an economic development scale - Saudi Arabia is less developed on a HDI.