They define the Legatum Prosperity Index™ as,
A true picture of the life chances for the world’s population, and the performance of nations, than any Index of GDP alone could hope to. True prosperity is as much about wellbeing as wealth and New Zealand, which tops the Index, is a model for delivering both.
The Index ranks nations over nine areas of potential success or failure: Economic Quality, Business Environment, Governance, Education, Health, Safety and Security, Personal Freedom, Social Capital and the Natural Environment.
I wasn’t able, in my brief reading, to understand whether the UK is improving it’s ranking. The report states that “Britain is flourishing, helped by a world-class performance in transforming wealth into prosperity”. While it notes “[it] is not good in making sure that prosperity reaches all.” You can use the report’s ranking comparison tool to find out more, or go direct to the UK’s section HERE.