I say this simply because there's long been a correlation between productivity growth and real equity returns. Good productivity growth in the early 1980s, early 1990s and late 1990s was associated with good returns, and productivity slowdowns in the late 1980s, early 2000s and late 2000s all saw shares suffer.
Of course, correlation doesn't establish causality. It might be that both equity returns and productivity are driven by changes in animal spirits; the same pick-up in confidence that raises share prices might also encourage companies to invest in productivity-enhancing equipment and techniques. It's also possible that an acceleration in technical progress for any reason would increase both optimism about shares and productivity.
However, it's also possible that faster productivity growth causes shares to rise. This is because it means that a given level of wage growth is associated with lower unit cost growth, which in turn means either that inflation - and therefore interest rates - stays low or that profit margins can rise. Either is good for shares.
In this context, the precedents of the recoveries from the early 1980s and early 1990s recessions are encouraging. Both saw productivity rise as previously underemployed workers worked harder. Both saw inflation fall. And both saw the share of profits in GDP rise, as high unemployment prevented workers from benefiting fully from the recovery.
What, then, could possibly go wrong? One possibility is that productivity doesn't actually recover, and that the supply pessimists are right to claim that the crisis did permanent damage to the UK's productive potential. One reason to fear this is that more recent labour market figures show an increase in hours worked in the May-July period, consistent with productivity stagnating again. If this happens over the longer term, a combination of falling unemployment and stubbornly high inflation would raise interest rates, while profits would struggle to rise as costs increase. This mix isn't great for shares.
But there's another danger, even if productivity does rise. It's that if we see profits rise the political backlash against years of falling wages might intensify. And as investors in utilities have learnt recently, this might have investment consequences.
For most of the last 30 years, we've thought of the political environment as generally favourable to shares while the macroeconomic climate hasn't always been so. It could be that the next few years see a reversal of this.
