Americans are looking forward to resting their bones. 

A University of Michigan index measuring whether they see a comfortable retirement -- compared with five years ago -- reached the highest level since December 2000 this month.

Despite recent market fluctuations, years of gains in equities have boosted the value of household retirement accounts: The S&P 500 Index has more than doubled since the survey’s last high through Feb. 14, and more than quadrupled since its recession low in March 2009.