Jeffrey Sachs writes:  The good news is that, even near the ZLB, monetary policy works. QE raises equity prices; lowers long-term interest rates; causes currencies to depreciate; and eases credit crunches, even when interest rates are near zero. The ECB and the BOJ did not suffer from a lack of reflationary tools; they suffered from a lack of suitable action.
The efficacy of monetary policy is good news, because fiscal stimulus is a weak instrument for short-term demand management. Ironically, in an influential 1998 paper, Krugman explained why. He argued at that time, and rightly in my view, that short-term tax reductions and transfers would be partly saved, not spent, and that public debt would multiply and create a long-term shadow over the fiscal balance and the economy. Even if interest rates are currently low, he noted, they will rise, thereby increasing the debt-service burden on the newly accumulated debt.

With all major central banks pursuing expansionary monetary policies, oil prices falling sharply, and the ongoing revolution in information technology spurring investment opportunities, the prospects for economic growth in 2015 and beyond are better than they look to the pessimists. There are rising profits, reasonable investment prospects for businesses, a large backlog on infrastructure spending almost everywhere in Europe and the US, and the opportunity to finance capital-goods exports to low-income regions, such as Sub-Saharan Africa, and to meet the worldwide need for investment in a new, low-carbon energy system.

If there is a shortfall of private investment, the problem is not really a lack of good projects; it is the lack of policy clarity and complementary long-term public investment. European Commission President Jean-Claude Juncker’s plan to finance long-term investments in Europe by leveraging relatively small amounts of public funds to unlock large flows of private capital is therefore an important step in the right direction.  Monetary Policy for Prosperity