40 of the richest US families pledge to donate at least half their money to charity.

Forty wealthy families and individuals have joined Microsoft Corp. co-founder Bill Gates and billionaire investor Warren Buffett in a pledge to give at least half their wealth to charity.

Six weeks after launching a campaign to get other billionaires to donate most of their fortunes, the chairman and CEO of Berkshire Hathaway Inc. released the first list Wednesday of people who have signed what he and Gates call the “giving pledge.”