A new report from the Employee Benefit Research Institute (EBRI), an independent nonprofit studying retirement issues, suggests many high-income people may have to adjust their standards during their golden years.

EBRI gathered data from 3,358 people who were between the ages of 55 and 64 in 2000. It compared their 2000 household income to their income in 2010, when everyone in the group had passed the traditional retirement age of 65. For this study, "income" included wages, pensions, and other retirement plan benefits as well as Social Security benefits. (The study excluded households with annual incomes of $1 million or more.)

The study showed a steep decline in income after retirement, with the median post-65 household collecting just 65.8% of the income it had earned before 65. But some interesting results emerged when EBRI dissected the data by income quartiles.

The income for households in the lowest quartile (median pre-65 income of about $23,000 a year) actually rose after 65 by more than 10%. People in the next quartile (pre-65 income of about $54,000) received about 80% as much income after 65 as before. But households in the two top quartiles, with median incomes of about $91,000 and $174,000 a year before 65, earned only 66% and 50% as much, respectively, after 65.

The lesson for top earners: Put extra effort now into retirement savings to avoid disappointment later.