The ranks of the world’s rich swelled to 8m during 2007 as the wealthy proved immune to the strains across global economies in the latter half of the year.

There was a 4.5 per cent increase last year in so-called “high net worth individuals”, those with investable assets of more than $1m excluding primary residence, according to the 2008 wealth report compiled by Citi Private Bank and Knight Frank, published on Monday.