There is no puzzle, it is a consequence of the "economic strategy" pursued by this government. It is inexcusable that large companies sit on billions in cash and run debts to buy shares back while everybody "waits" for the productivity to pick up as if it were either the employees' decision to work harder or a completely uncontrollable phenomenon like the wind. The employers are responsible for it, and the executives must put the cash to productive use.
This government seems to believe that cutting public expenditure will deliver some growth but all it has actually done apart from printing money was to funnel the economic resources into wealth accumulation at the top, mortgages and tax advantages for big business, with the net effect most people are worse off and have more debt.
Trickle down economics is a myth, it never worked and will not work simply because the capital owners have no incentive to pass on any of their gains. The perception that capital owners create jobs and wealth is nothing but a propagandistic metaphor because no products or services can be 'created' without labour. The only question is how fair is the distribution of the gains, and again, the perception that unless they get ever rising profits the rich elite will close the shop and go play golf all day long is false.
Without private and public investments it is impossible to have sustained growth and wide-spread well-being. The taxpayers are being taken for a ride and most people's lives have deteriorated. There is no need for more stats, and the explanations for this economic disaster don't even matter.
The government's 'economic trustworthiness' is a myth which is actually hard to explain, and one wonders what would it take to be broken.