The US M&A market saw a 20% leap in 2003 in the latest sign of a market comeback for corporate America, with New York leader Simpson Thacher & Bartlett emerging as last year’s top-ranked legal adviser.

The research, by Thomson Financial, underlines the returning confidence in the US M&A market, which saw a 19.6% value increase, up to $525.6bn (£291.1bn) from 2002′s $439.5bn(£240bn).