Demand has increased as investors seek alternatives to more than $10 trillion of debt globally thats yielding less than zero.
Performance fees in the second half are expected to be similar to the 1.2 million Swiss francs ($1.2 million) earned in the first six months of the year.
Money from brokers and independent advisers accounted for about 50% of the $225 billion Vanguard has brought in this year.
McNabb said investors pay an average of 12 cents per $100 for Vanguards mutual funds and ETFs and that in five years that number could fall below 10 cents.
Massachusetts Mutual Life Insurance, Pacific Life Insurance and TIAA are among companies that have been pursuing deals to diversify operations and gain market share from publicly traded rivals.