This metric aims to show the most competitive margin and idle cash rates at online brokers. These rates can make a big difference to your returns, more than whether a commission costs, say, $9.99 or $14.99.

Margin interest rates are rates you pay your broker if you borrow money to buy stocks. The rate generally varies depending on the amount you borrow. Smaller amounts usually draw higher interest rates, while substantial amounts generally command less interest. (For more on buying on margin, see this metric.)

Idle cash rates, often referred to as sweep account rates, refer to the rates paid on money that's idle in your brokerage account. This might be cash you transferred from another broker but have not yet invested or, say, cash proceeds from a stock sale. The chart above represents the basic rate for the basic account at that broker.

Idle cash rates can change daily, while margin interest rates change less often, typically when the Federal Reserve cuts or hikes interest rates. We publish both tables once a week.