How closely is wealth linked to health? In 2015, Qatar had the highest income per capita in the world while people living in Andorra had the highest life expectancy, living on average five years longer than the wealthy Qataris, to the ripe old age of 85.

Back in 1800, the wealthiest nation was the Netherlands, where people lived to almost 40 – the best average life expectancy in the world at that point, matched only by the Belgians.

So, with more than 200 years’ worth of data on income on the health and wealth of nations to analyse, how does income relate to life expectancy? The short answer: rich people live longer.

In the middle income countries, life expectancy ranges from just 50 in Swaziland to 75 in Vietnam. Several factors will affect these outcomes, including how the country’s wealth is distributed and how it is used.