Among them are that higher levels of labour turnover in a tight market disrupt productivity performance across firms; or that changed regulations (e.g. new accounting standards, tougher requirements to demonstrate appropriate corporate governance and so on) are using resources without adding to output.
At this point, however, these don’t seem sufficient as an explanation for a productivity slowdown of the magnitude we observe in the data. Hence it appears that, for the moment, we are left with something of a puzzle. That means that, as usual, monetary policy is being made under conditions of uncertainty.