(Bloomberg) -- BlackRock is cutting prices across its core ETFs in anticipation of a new U.S. rule that may prompt more investors to pour into passive funds.

The iShares lineup will feature lower expense ratios on 15 stock and bond funds aimed at buy-and-hold investors, BlackRock said Wednesday in a statement. Starting today the $80 billion iShares Core S&P 500 ETF, for example, will charge 4 basis points, or $4 a year per $10,000 invested, instead of 7, while the $42 billion iShares Core U.S. Aggregate Bond ETF will cost clients $5 instead of $8.

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