We conclude that a comprehensive policy effort to expand output is needed to sustainably raise private investment. Fiscal and monetary policies can encourage firms to invest, although such policies are unlikely to fully return restore investment fully to precrisis trends. More public infrastructure investment could also spur demand in the short term, raise supply in the medium term, and thus 'crowd in’ private investment where conditions are right. And structural reforms, – such as those to strengthen labor force participation, – could improve the outlook for potential output and thus encourage private investment. Finally, to the extent that financial constraints hold back private investment, there is also a role for policies aimed at relieving crisis-related financial constraints, including through tackling debt overhang and cleaning up bank balance sheets.
Explaining the Dearth of Private Investment @ Economist's View
Keynesian Multipliers, Investment Accelerators, and Crowding-in by DeLong
The IMF on Investment since 2008 by JW Mason