People Are Sharing 'Then And Now' Pics On This Page To Show How Time Changes Things (30 Pics)

Looking at some of these photos, human progress seems self-evident. City skylines keep expanding, people within them switch from horses to cars... But that's just the visuals. How do we actually calculate our advancement?

For this task, many use the Human Development Index (HDI).The HDI provides a single index measure to capture three key dimensions of our development: a long and healthy life, access to knowledge, and a decent standard of living.

The Human Development Index utilizes four key metrics: 1) life expectancy at birth – to assess a long and healthy life,

 2) expected years of schooling – to assess access to knowledge for the young generation, 3) average years of schooling – to assess access to knowledge for the older generation, 4) gross national income (GNI) per capita – to assess the standard of living.

In 2019, the United Nations Development Programme used the HDI to find out which countries are the most developed. The first place went to Norway, Switzerland came in second, and Ireland was third. The US tied the UK for the 15th spot.

Naturally, the HDI -- just like most similar metrics -- has been criticized. Mostly, for the alleged lack of consideration of technological development or contributions to human civilization. But it remains one of the most used measures worldwide to calculate how advanced countries are.