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.

There was particularly strong growth of wealthy populations in the emerging economies of China and India, as well as those countries that have access to ­natural resources such as Kazakhstan.

Countries such as Brazil, Canada, Australia and ­Russia also each added more than 8,500 wealthy residents in 2007 on the back of the commodity boom.

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The report says that the rate of growth of high net worth individuals has outpaced growth in both gross domestic product, and GDP per head, which it believes indicates that the rich are getting richer relative to their respective countries.

“This is not a perfect measure of relative wealth growth across income levels,” it says, “but there is an indication here that the ­plutonomy model retained its strength through 2007 and is in rude health.”

The US is still home to most of the world’s truly rich. High net worth individuals make up 1 per cent of the US population, with 3.1m people claiming to be dollar millionaires, and 460 to be billionaires.

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