Fidelity has overhauled UBS to become the world's largest investment manager by a slim margin, according to an annual survey of the world's top managers by consultant Watson Wyatt and US journal Pensions & Investments.

Fidelity ran assets worth $1.074 trillion (€1.21 trillion) at the end of December, according to the survey, representing an increase of 37%, thanks to market growth and sales of products in the US defined contribution and 401(k) areas.