Warren Buffett has topped a list of the 50 most generous billionaires in the US.

The Giving Index, produced by Condé Nast Portfolio magazine, ranks philanthropists by giving as a percentage of wealth.

Buffett features as the most generous and second wealthiest billionaire. He gave $46.1 bn (£27.1 bn) between 2002 and 2006 and has a net worth of $52 bn (£30 bn). His generosity in that period is over ten times that of the next philanthropist in the list, Bill Gates, who ranks as the wealthiest billionaire on the list with a net worth of $59 bn (£34.7 bn). Gates gave $3.7 bn (£2.2 bn) between 2002 and 2006.

Christy Walton was the highest ranking female philanthropist. A strong supporter of education and environmental charities, Walton has a net worth of $16.3 bn (£9.6 bn) and gave $3.5m (£2.1m) between 2002 and 2006.

In the UK, the Sunday Times Giving List ranks the 30 top philanthropists in the Sunday Times Rich List by their giving as a percentage of their wealth.