A new study says white Americans with low educational levels have already lost an average of four years from their life expectancy. That's the loss of 5 per cent of the average lifespan for an American who lacks a high school diploma, and it's happened at astonishing speed - between 1990 and 2008, says the lead investigator for the study, S. Jay Olshansky, a public health professor at the University of Illinois at Chicago. It compares to the much-deplored loss of life expectancy in post-Soviet Russia, when the collapse of the state-run system and an epidemic of alcoholism cut seven years from the life of the average Russian. While less-educated Americans were losing 5 per cent of their life expectancy, humanity as a whole went in the opposite direction, at about the same speed. Average life expectancy across the planet rose by 7 per cent from 1990 to 2010, according to UN data. "The reasons for the decline remain unclear, but researchers offered possible explanations, including a spike in prescription drug overdoses among young whites, higher rates of smoking among less-educated white women, rising obesity, and a steady increase in the number of the least-educated Americans who lack health insurance," summarises The New York Times' report of the study.

And the US overall was not doing very well by international comparison to start with. Americans rank 36th in the world for longevity with an average 78.3 years, almost identical to Cubans, who have one-fifth the level of income. Americans live 3½ years less than citizens of the five top-ranked countries - Japan, Hong Kong, Iceland, Switzerland and Australia. The story of American life expectancy is an alarming expression of its larger story. The US is delivering the full benefits of prosperity and modernity in an increasingly narrow way. It was long known that richer Americans improved their life expectancy at a greater rate than poor Americans, but lifespans lengthened for all. Today, advantaged Americans live longer while the disadvantaged live shorter. That is the real import of the new findings. It is about inequality, in the most basic manifestation - the number of days of life. Inequality is a subject American society has always found uncomfortable.

The Republican presidential candidate, Mitt Romney, with an estimated net worth of $200 million, is a case in point. Asked about inequality of wealth, Romney told the Today Show in January: "I think it's fine to talk about those things in quiet rooms … it's a very envy-oriented" approach. He did speak about it in a quiet room, during a private, $50,000- a-head fund-raising event. At least, he thought it was private until his remarks were leaked. He appeared to disparage the poor. Pointing out that that 47 per cent of Americans don't pay federal income taxes, Romney called them "victims" who have become dependents of the government. He said: "My job is not to worry about those people. I'll never convince them they should take personal responsibility and care for their lives." Romney thinks that inequality is not a concern for government. He's dead wrong. An impressive body of new research demonstrates that severe inequality aggravates problems all the way across the social spectrum.

And as equality improves, so does a society's performance in dealing with violent crime, depression, mental illness, obesity, educational failure and personal debt, among many other problems, as Richard Wilkinson and Kate Pickett showed in their groundbreaking book, The Spirit Level. The man Romney is challenging, Barack Obama, took the presidency determined to do something about the problem of America's glaring inequality. The US was the only developed country that didn't have universal healthcare. An estimated 40 million Americans had no health insurance. Obama set up a health reform program, nicknamed Obamacare, designed to bring healthcare within the grasp of many more people. It's not the sort of system of state benefits that other developed countries run - instead it forces more people to buy private health insurance. It's imperfect, but it's an improvement. "Socialism" was the catchcry, and it was the single biggest target of the angry Tea Party movement. But while Obama had the right impulse, he had lousy timing. He took office as the economy collapsed.

Income inequality in the US, already very skewed, has grown more unequal since the great recession of 2008. Before the recession, from 2002 to 2007, the richest 1 per cent enjoyed a generous 65 per cent of the gain in total national income. In 2010, it was a startling 93 per cent. Even the most committed Democrats are starting to despair. Joe Stiglitz, a Nobel Prize-winning economist and former member of the Clinton administration, writes: "Four years ago there was a moment where most Americans had the audacity to hope. Trends more than a quarter of the century in the making might have been reversed. Instead, they have worsened. Today that hope is flickering." The US needs stronger growth to generate jobs and wealth, and it needs to curb inequality so its citizens can enjoy the benefits. Instead it struggles with economic recession as well as social regression, and the outlook is dim, Republican or Democrat. Peter Hartcher is the international editor. Follow the National Times on Twitter