Investment services company Mercer has stolen a march on its rivals by merging with San Francisco-based peer Callan Associates, in a deal that cements its position as the largest investment consultant in the US, with an almost 20% market share.

Andrew Kirton, global head of Mercer Investment Consulting, said: "Mercer has a 10% share of the US market and is the largest investment consultant there, and merging with Callan almost doubles that. The US is a highly fragmented market for investment consulting; In the major markets elsewhere in the world, our market share is between 25% and 35%."