Seniors have lost 40 percent of their buying power since the beginning of the decade, according to a new study released by The Senior Citizens League, one of the nation's largest nonpartisan seniors groups.

Each year, seniors receive a small increase in their Social Security checks, intended to help them keep up with the costs of inflation. But since 2000, the Social Security Cost of Living Adjustment (COLA) has increased average benefits just 22 percent while typical senior expenses have risen by 71 percent, more than three times as fast.

A senior with the average Social Security benefit in 2000 received $816 per month, a figure that rose to $999.80 by 2007. However, that senior would require a Social Security benefit of $1,397 per month in 2007 just to maintain his or her 2000 lifestyle.

The study examined the increase in costs of eight key items between 2000 and 2007. The items were chosen because they are emblematic of the costs seniors must bear. Six of the eight costs exceeded the COLA – and three jumped by triple digits. The selected items represent five categories, weighted by approximate expenditure: food, housing, medical costs, transportation, and recreation.

"For years, we've been sounding the alarm bell that America's seniors are falling further and further behind, but even we didn't realize the situation was quite this stark," said Daniel O'Connell, Chairman of The Senior Citizens League. "If our annual Social Security increases don't keep up with inflation as they're intended to, how are we supposed to keep up with the rising costs of everything from prescription drugs to home heating to groceries?"

A majority of the 48 million Americans aged 65 and over who receive a Social Security check depend on it for at least 50 percent of their total income, and one in three beneficiaries rely on it for 90 percent or more of their total income. In general, low-income seniors are most affected by the loss of buying power, since they have few other sources of income.

To help increase buying power and offset the cost of Medicare Part B, The Senior Citizens League is lobbying for a change in the Consumer Price Index (CPI) used to determine the COLA. The government currently calculates the COLA based on the CPI for Urban Wage Earners and Clerical Workers (CPI-W), a slow-rising index that tracks the spending habits of younger workers who don't spend as much of their income on health expenditures.

However, the government does track the spending patterns of older Americans, and has done so since 1983 with the CPI for Elderly Consumers, or CPI-E. By tying the annual increase in the COLA to the CPI-E, seniors would see much needed relief in their monthly checks. For example, a senior who retired with a benefit of $460 in 1984 would have received almost $10,300 more over the past 23 years with the CPI-E.