The difference between the U.S. and most of the rest of the world “is very stark,” said Jonathan Skinner, a professor of economics at Dartmouth College.

Newborns in 29 countries, including Japan, Australia and Spain, had life expectancies above 80 years in 2015, according to the World Health Organization. The average global life expectancy was 71.4 and rising, according to that agency’s most recent report.  

If only the good die young, Americans are unfortunately getting better.

U.S. life expectancy dipped by a little more than a month last year from 2014, to 78.8 years, according to a report from the National Center for Health Statistics. It's the first decline in more than two decades. And after years of gains, U.S. life expectancy has been essentially flat for a few years, which means an inauspicious trend could be in the works.

The decline "could be a blip, but even if it’s flat, we have a real problem," said Jonathan Skinner, a professor at the Dartmouth Institute for Health Policy & Clinical Practice.