Principal author Justin Denney of Rice University and colleagues said the average life U.S. expectancy for a person born today is 78.49 -- significantly lower than for people born in Monaco, Macau and Japan, which have the three highest life expectancies at 89.7 84.4 and 83.9 years, respectively.
In addition, the poorest U.S. citizens tend to live five years less than their more affluent countrymen, Denney said.
The study, scheduled to be published in the Social Science Quarterly, found average life expectancy in the United States rose from 59.85 years in 1930 to 77.1 by 2000.
"But when broken down, these numbers show that those gains were mostly experienced between 1930 the 1950s and 1960s. Since that time, gains in life expectancy have flattened out," Denney said in a statement. "During periods of expansion in length of life, a similar expansion has occurred between more and less advantaged groups -- the rich get richer, the poor get poorer, inequality grows and life expectancy is dramatically impacted."
Despite disproportionate spending on healthcare -- U.S. healthcare costs more than double that of the second-most expensive healthcare -- U.S. life expectancy continues to fall down the ladder of international rankings of length of life, Denney said.
"It goes to show that prosperity doesn't necessarily equal long-term health," Denney said.
Notable deaths of 2014 [PHOTOS]