How much do you have saved for retirement? If it's $5,000 or more, you're doing better than about one-third of Americans. That's the depressing result of a new Northwestern Mutual survey of more than 2,000 people. In the survey, 21 percent said they had zero in retirement savings, and another 10 percent had less than $5,000.

Of course, some of these may be young people who are just getting started, saving to buy a home, starting a business, or just haven't thought much about retirement yet. But even among Baby Boomers, currently 53 and older, one-third have retirement savings of $25,000 or less.

Why aren't people saving more? When Northwestern Mutual asked that question, more than a quarter of respondents said their income had either declined or stayed the same as the previous year, a surprising finding in a booming economy where unemployment is at a historic low. Another 16 percent said they were saving for something else instead, and 12 percent said their expenses were up and they couldn't afford to save. Another 21 percent either said they hadn't gotten around to it or just didn't answer the question. Five percent said they'd encountered an unexpected financial emergency that prevented them from saving. Only 21 percent said they were satisfied that they had saved, or were saving, enough already.

If Americans aren't saving enough for retirement, at least most seem to have few illusions about what that means for the future. The survey found that 78 percent of respondents were "somewhat" or "extremely" concerned about being able to afford retirement. And so most of them expect to keep working. More than half, 55 percent, expected that they wouldn't retire at 65, and 38 percent expected they'd have to work until 70 or older.

Of course, some people plan to work past 65 because they love their jobs, but fewer people seem to feel this way than in the past. In earlier surveys, of those who thought they'd work past 65, two-thirds gave "professional satisfaction" as the main reason. In the latest survey, that number was down to 54 percent.

Meanwhile, 61 percent said they expected their Social Security payments wouldn't be enough to cover their needs. And 52 percent worried that runaway expenses, such as medical costs, would keep them from retiring.

Average retirement savings: $84,821

Some people do have more substantial retirement savings. More than a third of respondents had at least $75,000 saved for retirement, and a quarter said they had $200,000 or more. Overall, of those who had retirement savings, the average was $84,821, the survey found.

Of course, even $200,000 isn't enough to provide much of a retirement. Most experts have traditionally recommended at least $1 million to fund a comfortable retirement. But these days, when interest rates are very low, you can't count on even $1 million generating enough to get you through a retirement. The personal finance site GOBankingRates did a study comparing how long $1 million would last in each state, and found it would be spent quickest in Hawaii (about 12 years) and slowest in Mississippi (about 26 years). On average, their research found, you would expect to run through $1 million in about 22 years. GOBankingRates didn't take into account any Social Security payments or earnings from investing the $1 million before it is spent, so things may not be quite as dire as they seem. On the other hand, they also didn't take into account any expenses beyond the basics of housing, groceries, utilities, transportation, and health care.

What do you think? Will you have enough to get you through retirement? If not, it's time to start saving more now. If you can't, consider following Tony Robbins's very simple advice: Next time you get a raise or otherwise increase your income, take that additional money and put it into retirement savings. Since you didn't have it before, you won't miss it, and you won't have to give up anything to set it aside.