US Senate hearing this week will focus on outsized voting power of index tracking funds

BlackRock clients are taking more control of the way their shares are voted on hot topics such as climate change and executive pay, as pressure mounts on the largest asset managers over their outsized power at US companies.

BlackRock said on Monday that the owners of more than $530bn invested in its index tracking funds are now instructing the firm how they want their voting power exercised. While some large clients have had this ability for years, the holders of $120bn more have signed up in the five months since BlackRock rolled a new Voter Choice programme.

BlackRock made the figures public ahead of a Senate hearing this week on the voting power of index tracking funds, which manage more than $11tn. BlackRock, State Street and Vanguard, the largest providers, are the biggest shareholders in most US companies.

Read more: FT