This has to do with the generally low levels of investment in the Scottish economy, which stands at about half that of our main competitors - not such good news because this would tend to lower productivity.
I don't claim to know the solution but from past form, having the Executive throw money at the problem is a) unlikely to work b) nevertheless the most likely outcome.
Cue the nationalists with the One Answer and much talk of 'Celtic Tigers' and stuff. Maybe if they could be a bit clearer as to what they would do specifically with fiscal autonomy that would make the Scottish economy more tigerish and emeraldy, they might get on a bit better. In fairness, the SSP have been the clearest here about their post-independence economic plan - but since this plan seems to consist of going for the Soviet model - Cuba without the sun and cigars - this isn't much help.