您正在看的时事英语是:美高负债家庭面临升息之苦。 a. But most of the debt is at fixed interest rates. Thus it will be unaffected initially as the central bank begins its much eXPected quarter-point increases in the so-called federal funds rate, now at a 46-year low of 1 percent. The federal funds rate, in turn, influences the interest rate cost of most household and commercial debt.

Only one-fifth of the $9 trillion in total household debt, or $1.8 trillion, is borrowed at variable rates. Variable rates, like those that the Diffenderfers pay on their four credit cards, often track what the Fed does, which means they are likely to rise one-quarter of a percentage point over the next few weeks. The immediate cost for the nation's households as a result of this process could be as much as $4.5 billion, including the initial $35 increase in the Diffenderfers' monthly credit card bill.

The $4.5 billion is roughly 10 percent of the cost of the rise in oil prices so far this year. That is not a big number yet, but each quarter-point increase would be another step closer to matching the oil shock, which brought gasoline prices above $2 a gallon in many parts of the country.

While the oil shock quickly raised the gasoline and heating oil bills of nearly every household, the burden of higher interest payments falls most heavily in the early stages on lower- and middle-income families. They are the biggest users of variable rate debt, particularly on credit cards, various studies show.

Upper income families, on the other hand - that is, families with more than $80,000 in annual income - are more likely to have fixed rate debt, particularly mortgages, and to owe relatively little on their credit cards. What variable rate debt they do have is usually at lower interest rates than lower income people. Lower income people, as a result, are 10 times more likely than upper income people to be devoting 40 percent or more of their income to debt repayment, the Economic Policy Institute reports. In addition, upper income people are the nation's biggest savers, and a rate increase raises the return on their interest-bearing securities.

"If you are a household with a lot of variable-rate debt and little equity left in your home that you have not already borrowed against, this is going to be a scary time," said Mark Zandi, who is the chief economist at Economy.com.

The Diffenderfers have a combined income of nearly $70,000 a year, incl