But McWilliams is sceptical of this, arguing that QE increased the total available pool of capital in the world, which should mean that both the productive and unproductive companies can easily access capital, and in that scenario, the most productive companies should still be able to take market share from those that are least productive, driving up the overall level of productivity in the economy.

Baker’s view is that while the impact of QE on productivity is likely to be profound, she says it may be some time before it is evident from the data what that impact has been. 

While GDP data tends to track wider business and market cycles and can be wildly volatile, productivity growth is something the pattern of which evolves more slowly over time, but is a much greater determinant of long-run economic and investment market performance, and so will be crucial to the outcomes for advisers and their clients in the years ahead.   

David Thorpe is investment editor of FTAdviser