Human Development Index (HDI) – A method of measuring development in which GDP per capita, life expectancy and adult literacy are combined to give an overview index figure

Note: Per capita is a Latin term that translates to "by head". So per capita means the average per person.

This human didn't develop their index (human development index) finger. The index finger is used to indicate where to go, to point, but here it's missing.

Human Development Index is a combination of: 

To remember these elements, we need to go back to the hand again and look at the remaining fingers.

To remember that one finger deals with the amount of money a country has: 

Your ring finger is the finger next to the little finger, on which the engagement and wedding rings are worn. Some people spend massive amounts of money on these rings.

The middle finger can help you to remember middle age. Will you reach middle age? What's your life expectancy?

Middle finger - middle age
Life expectancy - will you reach middle age?

The little finger will help you remember education is also one of the criteria used in the Human Development Index.

How many books can your little finger lift in one go?
Books = education.

Summary

The Human Development Index is a combination of:

Ring finger = diamonds = money (standard of living)

Middle finger = will I reach middle age? = life expectancy

Little finger = books = average education level

Is GDP a true reflection of a nation's economic and social wellbeing?
The Human Development Index was developed because there is a very uneven distribution of wealth in some countries such as Qatar and The United Arab Emirates. A nation's wellbeing is not reflected in the country's GDP figures alone.

If the people in a country have excellent healthcare with few baby deaths and long life plus excellent and long education, this, people believe, is a better reflection of a nation's wellbeing.

The Human Development Index runs from 0 to 1, with 0 being the worst and 1 being the best.

Examples

The USA had an HDI in 2011 of 0.91
Niger in Africa had an HDI in 2011 of 0.295

Even if a nation has a high figure, there is no reflection of how happy a nation is or if it has excellent human rights.
In a vast country like China, the HDI in regions within the country can vary enormously.