IN THE aftermath of the 2016 presidential election, much blame was heaped on social media for fuelling partisan rancour. Even Mark Zuckerberg, the boss of Facebook, considered the idea that social media may have enabled the spread of "fake news" and helped exacerbate political polarisation. But recent analysis suggests that the part of the electorate that has become more polarised is not one commonly associated with social media platforms, but old people. And social media may provide a partial solution.

The authors of the report, Levi Boxell, Matthew Gentzkow at Stanford University and Jesse Shapiro at Brown University, accept there is strong evidence of growing polarisation in terms of measures like "straight-ticket" voting: selecting one party’s candidates for every race on the ballot. But they argue that demographic evidence points away from social media as a cause. Social media use is concentrated amongst young people—around four out of five adults under the age of 40 used applications like Facebook and Twitter in 2012 compared to one in five of those above 65. The polarisation problem is concentrated amongst older voters. For adults under the age of 40, there is very little evidence of growing polarisation between 1996 and 2012 while there is a dramatic increase amongst those 75 and older. The polarisation amongst the old will have been skewed towards the right: 55% of voters above the age of 65 voted for Donald Trump compared to 31% of those aged 18 to 29.

Between 2010 and 2050, the proportion of America's population that is over 65 will increase from 13% to 21%. That will leave the whole country looking like Florida does today. And it will have a dramatic impact on health-care costs, social security spending and economic performance. Population ageing is linked to lower labour productivity and labour force participation. Nicole Maestas, Kathleen J. Mullen and David Powell, writing for the National Bureau of Economic Research, estimate that America's annual GDP growth will slow by 1.2 percentage points this decade and 0.6 percentage points next because of it.

And yet, older voters are likely to stand in the way of bipartisan fixes to the economic problems that an aging population helps to exacerbate. For example, older people are among the groups most opposed to health-care reform. It is hardly surprising that older voters are also considerably less likely to think that social security and Medicare spending might be too much of a financial burden on younger generations according to Pew polling. Old people are also opposed to perhaps the most straightforward fix to aging populations and low growth: importing young working-age people with comparatively high fertility rates.

Indeed, Glenn Rayp of Ghent University and colleagues Ilse Ruyssen and Samuel Standaert find that as populations age, countries are more likely to restrict immigration. They suggest “the voting behaviour of the elderly is driven less by economic considerations—i.e. the (partial) relief immigration might provide to cope with the burden of an aging population—but rather dominated by other motivations or cultural concerns.” This certainly applies in the case of America: according to Pew surveys, 76% of those born after 1980 suggest immigrants strengthen the country compared to 41% of those born between 1928 and 1945.

If younger people are to ensure that the current generation of retirees doesn’t imperil their future, they need increased political clout. And here, much-vilified social media might provide part of the answer. Voter turnout among voters aged under 30 run as much as twenty percentage points below turnout for the over-60 age group. The internet can help close that gap. Michael Xenos of the University of Wisconsin-Madison with his colleagues Ariadne Vromen and Brian Loader studied social media use across Australia, Britain and America. In all three countries they found that social media use among young people is associated with greater political engagement. Perhaps, then, Facebook can help ensure that America is still great when millennials are retiring.