A small proportion of US trading firms are using computer-driven strategies to control three-quarters of equity trades and generate $21bn (€15bn) in annual profits, according to a new report, which puts a figure on algorithmic activities for the first time and highlights the significance of this week's alleged theft of code from Goldman Sachs.

High frequency traders, which represent just 2% of the 20,000 US trading firms, have made rapid inroads into the nation's equity markets in recent years, increasing their market share to 73% this year from 30% in 2005, according to research firm Tabb Group.