Nearly one in two Americans — 46 percent — die "with virtually no financial assets," or less than $10,000, according to a recent study by economics professors at MIT, Dartmouth and Harvard. In fact, 19 percent of Americans die with "zero" financial assets, the study found.

The study found that many of these people with modest assets rely "almost entirely" on Social Security benefits to survive, own no housing property, and are in poor health. People with zero financial assets and an annuity income of less than $30,000 were in the bottom health quartile before they died, while those in households with financial assets of at least $25,000 and an annuity income of $30,000 to $40,000 were in the 43rd health percentile before they died, according to the study.

Poorer Americans die younger, in part because they cannot pay for medical emergencies, according to the study. And before death, poorer Americans' quality of life is significantly lower than the quality of life of their richer counterparts.

Many of these Americans who die without assets in effect outlive whatever retirement savings they may have.

Most Americans do not save enough, and half of Americans are not saving at all for retirement, according to a recent study by LIMRA, a financial services trade association. Younger people are particularly unlikely to save for retirement, in part because many have less financial education, lower earnings and student loan debt.

Americans need about $1 million in retirement savings to generate $40,000 per year in retirement income, according to Kiplinger. So it is best to start saving early.