<p><b>Bill Gates, philanthropist, Microsoft co-founder and chairman speaks at MIT in Cambridge, Massachusetts</b> <p></p><p> <p>Things are on the up for US billionaires with more than half of them adding to their net worth in a year which once again saw Bill Gates as the richest of them all, Forbes magazine said on Wednesday. <p></p><p> <p>Gates, founder of Microsoft, was the richest person in the United States for the 17th year in a row with an estimated worth of $54 billion, up $4 billion from last year. <p></p><p> <p>No. 2 on the list was investor Warren Buffett, worth $45 billion, up $5 billion. Oracle founder Larry Ellison's net worth was unchanged, in third place, at $27 billion. Christy Walton, heir to Walmart founder Sam Walton's fortune, was in fourth place with $24 billion, up $2.5 billion. <p></p><p> <p>In stark contrast to the 2009 Forbes 400 list, 217 of the tycoons are now worth more than they were a year ago. Just 84 of the billionaires had a decrease in wealth. <p></p><p> <p>In 2009 a whopping 314 members of the exclusive club had experienced a decrease in their wealth. <p></p><p> <p>The top 10 gained $24.9 billion. The same group had shed almost $40 billion last year. <p></p><p> <p>Four Indian-Americans form the part of the list. <p></p><p> <p><b>(Pictures by Reuters)</b> <p></p>