The world’s problem since the subprime crisis: Inefficient or insufficient investment

At the global level since the subprime crisis: Labour productivity has slowed, leading to lower potential growth; Yet total and private investment rates have risen; Higher investment rates have been made possible by an increase in the private sector savings rate, only some of which has been absorbed by an increase in the fiscal deficit excluding public investment. Why has the increase in investment made possible by the increase in private savings not led to faster productivity gains? First possibility: the increase in the gross investment rate has not been sufficient to prevent a fall in the net investment rate after capital depreciation, leading to slower growth in net capital. This might result from faster capital obsolescence; Second possibility: investment has been less efficient, so its higher level has not increased labour productivity.