More than half of American households are at risk of being unable to maintain their preretirement standard of living in retirement, according to new estimates from the Center for Retirement Research.

To arrive at that conclusion, the center used data in the Federal Reserve's 2013 Survey of Consumer Finances and "compared projected replacement rates — retirement income as a percentage of preretirement income — with target rates that would allow (SCF households) to maintain their living standard and calculated the percentage at risk of falling short." 

In its data-crunching, the center took into consideration that people typically need less than their full preretirement income once they stop working, since they generally pay less in taxes, no longer need to save for retirement, and often have paid off their mortgage.