As had been trailed, the OBR cut its forecasts for productivity growth and hence GDP growth yesterday. Here are some miscellaneous thoughts on this.

1. If the OBR is right, this means the 20 years to 2022 will see the worst productivity growth since 1891-1911, and close to the slowest growth since the early 1800s.

2. The OBR might not be right. It says there's "huge uncertainty" about its forecasts. One reason for this is that we don't really have a terribly robust theory for forecasting such growth. The OBR's past forecasts were too optimistic because it essentially assumed growth would return to trend. We know that was wrong. But we don't really have much better ideas.

3. The ONS estimates that productivity grew 0.9% in Q3. That's inconsistent with the OBR's forecast of zero growth this year - but it is little more than a straw in the wind.

4. Weak productivity growth isn't wholly a bad thing, as it keeps people in jobs. As Amit Kara and Ana Rincon-Aznar point out, there has been a negative relationship between employment and productivity. Granted, this trade-off might be the result of bad macroeconomic policy. But bad macro policy is what we've got.

5. There's a significant difference between the UK and US. In the US the main reason for flat real wages has been that monopoly power has risen and the labour share has fallen. In the UK, the labour share has been reasonably stable recently; the main reason for weak real wages is weak productivity.

6. History tells us that productivity growth has really only been much above 2% during the post-war era. This poses the question: to what extent was that growth due to us catching up on innovations which had been delayed by the war, and to what extent to the possibility that neoliberalism in fact retards productivity growth? A lot hinges upon this question of economic history.

7. If productivity and income growth remains weak, future governments will have to look elsewhere for revenues. The possibility of taxes on wealth (as advocated by Roger Farmer) or land thus loom larger.

8. Robert Colville - who's more sympathetic to Hammond than I - says there "was little sign of a serious assault" on the productivity problem in the Budget. He's right. For example, the National Productivity Investment Fund won't launch until 2022.

9. We don't really know the precise causes of the productivity slowdown. There are many contenders. I'm not sure, though, that we need to know for policy purposes. I'd advocate a broad spectrum approach of many measures such as: policies to encourage investment and innovation, which might range from tax reform to a state investment bank; more infrastructure spending; better education and training; greater worker democracy; an attack upon rent-seeking and measures to raise entry (pdf) and exit in product markets. Most of these policies are worth doing even if their impact on productivity is slight.

10. Duncan Weldon tweeted:

I suppose a small open economy slashing its growth forecasts even as global growth picks up at least shows that policymakers aren't powerless in this globalised world.

But maybe their power is asymmetric. Governments with trend growth rates might be like monkeys with computers: they can't improve them, but they can wreck them.