BlackRock is pulling some $2tn of assets out of State Street’s safekeeping, a move that will reduce the investing firm’s reliance on a small number of parties and lower the fees it pays for back-office work.

For more than a decade, State Street served as the sole custodian to BlackRock’s US exchange-traded funds — low-cost investment vehicles that have exploded in popularity in recent years. State Street services all of the roughly $2.3tn across those BlackRock funds.