The juxtaposition of David Cameron's claim that we have a "fundamental duty" to care for pensioners with the FT's story that 20-somethings have low incomes after housing costs reminds us that intergenerational justice is now a big issue.

But I wonder: is this partly a product of secular stagnation?

To see my point, consider a reasonably typical exchange between a youngster and oldster:

Oldie: You guys are lucky. You have smartphones, tinder, spotify and free books and music - and less sexism, racism and homophobia than in my day.
Youngster: But I can't afford anywhere to live.

The oldster is telling a story about progress, the youngster one about diminishing returns: you can think of high house prices as evidence of Ricardo's claim that economic growth would raise land prices and rents.

In fact, you can think of economic history as a fight between diminishing returns and technical progress. Diminishing returns reduce productivity and raise relative prices; technical progress raises productivity and reduces relative prices.

Now, if technical progress wins the race, things look dandy for youngsters. We can tell them:

You'll enjoy many more new technical breakthroughs that we oldsters won't live to enjoy. You should also see rising real incomes. And because productivity rises, the "triple lock" on pensions will be sustainable. This means it will benefit you more than today's oldies - simply because 50 years of rising real pensions is better than ten years of them. It's even possible that teleworking will depress house prices in future in the same way that the spread of commuter railways did before WWII, so you needn't worry about high house prices. Heck, you might even get to live very much longer - and this beats everything.

If, however, diminishing returns win out, then this doesn't apply. Instead, youngsters face stagnantish real incomes and more unaffordable housing, whilst generous state pensions will prove to be unsustainable.

This is what I mean when I say that intergenerational justice is on the agenda now in part because of secular stagnation*. It's the threat of this that gives youngsters a grievance.

You don't have to be a Marxist to see that the economic climate influences social and political issues: as Ben Friedman showed, booms make people tolerant and slumps make them racist and mean. What we're seeing with intergenerational justice on the agenda might just be an example of how stagnation is shaping politics. There might well be other examples to come - and Friedman's work suggests they'll not be nice.

* Rick might be right to say that stagnation represents a return to normal. For example, according to Angus Maddison's data, UK real GDP per capital grew only 1.3% pa between 1830 and 1913. On the other hand, though, this might be the final crisis of capitalism.