A lousy week on Wall Street didn’t have much effect on mortgage rates.

Stock prices fell to 12-year lows, with the Dow Jones industrial average falling below 6800. Normally, a giant slide on stock prices is met by a plunge in mortgage rates. But not this time. Mortgage rates are low already, and they resist falling further.

The benchmark 30-year fixed-rate mortgage was unchanged, at 5.41 percent, according to the Bankrate.com national survey of large lenders. The mortgages in this week’s survey had an average total of 0.41 discount and origination points. One year ago, the mortgage index was 6.32 percent; four weeks ago, it was 5.7 percent.

The benchmark 15-year fixed-rate mortgage rose 1 basis point, to 4.94 percent. A basis point is one-hundredth of 1 percentage point. The benchmark 5/1 adjustable-rate mortgage fell 1 basis point, to 5.39 percent.

Weekly national mortgage survey
Results of Bankrate.com’s March 4, 2009, weekly national survey of large lenders and the effect on monthly payments for a $165,000 loan:
30-year fixed 15-year fixed 5-year ARM
This week’s rate: 5.41% 4.94% 5.39%
Change from last week: N/C +0.01 -0.01
Monthly payment: $927.56 $1,299.66 $925.50
Change from last week: N/C +$0.86 -$1.03

The federal government keeps reiterating that it’s keeping rates low by buying mortgage-backed securities. Here’s how the Treasury phrased it Wednesday morning: “The Treasury Department increased its funding commitment to Fannie Mae and Freddie Mac to ensure the strength and security of the mortgage market and to help maintain mortgage affordability.”

Over and over, the Treasury and Federal Reserve keep sending messages similar to this. Because mortgage rates haven’t changed a heck of a lot since December, it doesn’t take Sherlock Holmes to deduce that the feds have mortgage rates where they want them — around 5.5 percent, give or take a quarter of a percentage point.

Yet mortgage brokers and lenders say that their clients keep holding out for even lower rates. Last fall, the National Association of Realtors tried to persuade the Fed and Treasury to use the taxpayers’ billions to bring mortgage rates down to around 4 percent. The Fed and the Treasury never endorsed the idea.

That point was lost among many news consumers: The Fed and the Treasury never said they were going along with the notion of cutting mortgage rates to 4 percent. But readers and viewers got that impression, anyway. The “4 percent solution” was a scheme cooked up by lobbyists, but many would-be borrowers are under the impression that the idea originated with the feds.

Now more uncertainty has been brought into the mix. The Obama administration released details of its foreclosure-prevention program on Wednesday, but few details were forthcoming about the eagerly awaited refinancing plan.

The refinancing part of the Making Home Affordable plan envisions allowing borrowers to refinance their conforming mortgages, even if they owe what the house is worth. Wednesday’s announcement shed little light on exactly who would be eligible for refinancing under this program.

One thing is clear: “Refinances in process are not impacted by this,” says Dan Green, loan officer for Mobium Mortgage in Cincinnati. “If you have a loan in process, continue with that.”