You probably know that a reputable brokerage will typically "sweep" any extra money you've got lying around in your portfolio (that is, dollars not currently invested in any stocks or funds) into an interest-bearing account. Sounds good, eh?

But the brokerages don't treat all of us the same. The more money you have at the brokerage, the better interest rate you'll likely receive. It doesn't sound quite fair, does it?

An October article in The Wall Street Journal reviewed this development, noting that some brokerages are creating many different "tiers" of customers, each earning different rates, while others are simply lowering the rates for their lower-tier customers and raising them for their most lucrative ones. The logic behind it all is profits. Firms are choosing to offer their best service to their best customers -- those who generate the most money (often simply by having the most money). Whereas before, more customers would get their excess money invested in money market accounts, now less attractive customers are having their money invested in more standard bank accounts in the brokerage's banking division -- which permits the brokerage to then lend that money out and profit on it.

The Journal reported: ".investors with less than $100,000 in assets often can end up earning about 1% or less on their cash, which is less than a third of what most money market mutual funds are currently paying. Even larger investors need a sizable amount of money -- often over $1 million -- in order to qualify for rates that are comparable to those being paid on taxable money market mutual funds."

It offered some examples:

  • "Merrill Lynch (NYSE:MER) recently changed the tiers on its accounts so that investors with total assets below $250,000 now earn the firm's lowest rate of interest on their parked cash."

  • "Charles Schwab (NYSE:SCH) this summer increased to nine from five the number of interest rate tiers it employs, with its lowest tier of below $10,000 in total assets yielding 0.5%."

  • "E*Trade (NYSE:ET), which paid a flat rate of 0.4% until last spring, now has four tiers with yields starting at 0.16%."

  • "Morgan Stanley (NYSE:MWD) plans to implement a tiered structure when it shifts some of its clients' cash to bank-sweep accounts from money market funds later this year."

So what can you do? Well, your best bet is to stop being a small investor and become a wealthy one. If that doesn't seem too possible in the near future, consider consolidating accounts. If you have $50,000 at one brokerage and $60,000 at another, you may benefit by bringing all your investments under one roof.

Another option? Just shop around a little more. There may well be another brokerage that serves your particular needs better. Pop into our Broker Center for lots of guidance on how to find a better brokerage, including our handy comparison table.

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Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article. She recently discovered that there's a sink that bears her name. Charles Schwab is a Motley Fool Stock Advisor pick. The Fool has a disclosure policy.