(Bloomberg) -- Another day, another shot across the bow.

Fidelity Investments is lowering online commissions for trading in U.S. stock and ETFs by nearly 40%, to $4.95 from $7.95 a trade, for individual investors. The nation's largest online retail brokerage firm, with 17.9 million accounts and $1.7 trillion in client assets as of Dec. 31, is also cutting options pricing, to 65 cents from 75 cents a contract, and lowering margin rates for investors.

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