What Is Assets Under Management (AUM)?
Assets under management is the total value of all the capital an investment firm oversees for its investors. For a mutual fund or hedge fund, it is the market value of the portfolio; for a private equity firm, it usually includes both invested capital and committed capital that has not yet been called from limited partners.
AUM changes for two reasons: investment performance moves the value of existing holdings up or down, and investor flows add money through new subscriptions or remove it through redemptions and distributions. A firm can grow AUM by performing well, by raising new funds, or both.
How AUM Drives Fees
AUM matters because management fees are charged as a percentage of it. A firm charging 2% on $10 billion of AUM collects $200 million per year regardless of performance, which is why asset gathering is such a powerful business model. This is also why fee rates and AUM composition are scrutinized: 2% on a private equity fund is very different from the 0.03% an index fund might charge.
Definitions vary across the industry, so comparisons require care. Some firms report gross AUM including leverage, others report net; private markets firms often highlight fee-earning AUM, the portion actually generating management fees, as the cleanest measure of revenue potential.
Example
Suppose a hedge fund starts the year with $4 billion in AUM. Its portfolio returns 10%, adding $400 million, and investors contribute a net $600 million of new capital. Year-end AUM is $5 billion, and if the fund charges a 1.5% management fee, next year's fee revenue rises from $60 million to $75 million.
At the industry's largest scale, a manager like BlackRock with roughly $10 trillion in AUM earns enormous revenue even at very low fee rates, illustrating how AUM and fee percentage trade off against each other.
Why It Matters
AUM is the headline number used to rank and compare investment firms, and growth in fee-earning AUM is a key metric for publicly traded asset managers like Blackstone and KKR. For anyone interviewing in asset management or private markets, knowing a firm's approximate AUM and flagship funds signals genuine preparation.
AUM also shapes strategy: as funds grow larger, they must write bigger checks and pursue bigger deals, which can change, and sometimes dilute, the returns that made them successful at a smaller size.
