BOSTON – Almost 45% of working-age households are "at risk" of being unable to maintain their pre-retirement standard of living in retirement, according to the new National Retirement Risk Index developed by the Center for Retirement Research at Boston College. Younger households are particularly vulnerable, as are those with low incomes or no pensions, the index revealed. The reason for this gloomy picture is a rapidly changing retirement landscape defined by a rising Social Security retirement age, a sharp decline in traditional pensions coupled with modest 401(k) balances, low savings rates, and longer life spans. The index projects how much income households are expected to have in retirement relative to their pre-retirement income. It then compares this "replacement rate" to a target rate that would allow a household to maintain its pre-retirement standard of living. Households that fall more than 10% short of the target are considered "at risk." Conservative assumptions are used and therefore may actually understate the size of the retirement challenge, according to CRR. The index also assumes that households take full advantage of their available assets by purchasing an annuity with their financial wealth and taking out a reverse mortgage to tap their housing equity. Finally, the index requires that household replacement rates only come within 10% of the target, not actually hit it. "Unless Americans change their ways, many will struggle in retirement," said Alicia Munnell, CRR director.