Accountants EY say that the number of firms issuing profit warnings has risen. This reminds us of an awkward fact - that real wages haven't fallen because capitalists have increased their exploitation of workers. Instead, they've fallen because productivity has fallen. And lower productivity means lower incomes for both capital and labour.

My chart shows the point. It shows that the share of non-financial profits in GDP hasn't changed much since 2010, and is lower than it was before the crisis.

This doesn't necessarily undermine Labour's interest in predistribution and the Left's interest (pdf) in wage-led growth. Solutions to problems need not resemble their causes. Even if a fall in labour's share of GDP isn't the main cause of falling real wages, a higher wage share might boost growth - though I have my doubts.

Not least of such doubts is whether such a shift is achievable. A new paper by David Bell and Danny Blanchflower argues that "the UK labor market is much further from full employment than the MPC calculates". If they're right, there'll be continued downard pressure on wages. Which means predistribution will be fighting against the tide of market forces.

What can be done? There are two (non-exclusive) possibilities.

One is to raise productivity growth; if the pie grows, everyone could, in principle, get a better slice. This, though, runs into two problems: we don't know why productivity has stalled - the Bank of England calls it a puzzle (pdf); and history shows that national policies can't do much to raise trend growth.

The second possibility is simply to increase aggregate demand through looser fiscal policy; this would help reduce labour market slack and downward pressure on wages whilst also boosting profits, so both capital and labour win. This, though, is excluded by Labour's commitment to austerity.

I fear, therefore, that there's not much that economic policy will do to raise real wages.

Complaining about this fact is, however, as futile as complaining about the poor quality of modern pop music. Given the twin constraints of poor public taste and the interests of capital, we should not expect anything better.