The takeaway from six years of economic troubles? Keynes was right.:

Countries that took emergency measures to reduce public borrowing have mostly suffered weaker growth, as in the case of Britain from 2010 to 2012, Japan this year and the United States after the 2013 “sequester” and fiscal cliff deal. In more extreme cases, such as Italy and Spain, fiscal tightening has plunged them back into deep recession and aggravated financial crises. Meanwhile countries that ignored their deficit problems, as in the United States for most of the post-crisis period, or where governments decided to downplay their fiscal tightening plans, as in Britain this year or Japan in 2013, have generally done better, both in terms of economics and finance.

But this is the key quote:

Monetarism overturned the Keynesian fiscal consensus that prevailed from the 1930s to the 1970s, by introducing one simple assumption into the models that guided governments and central banks. The case for Keynesian fiscal stimulus in deep recessions was simply assumed away by asserting that interest rates could always be reduced sufficiently to stimulate private investment, discourage private savings and so restore growth. As a result, the private sector as a whole would never suffer for long from a shortfall in spending. Therefore government borrowing would never be needed to balance inadequate private demand.

As a result of these assumptions, interest rate decisions by central banks came to be seen as the only effective tool of macroeconomic management, while fiscal policy was relegated to a microeconomic supporting role. Tax structures and public spending levels were seen as supply-side issues influencing incentives and resource allocation, but the demand impact of government borrowing was largely ignored. Whether government borrowing expanded or contracted, interest rates would rise or fall to offset the Keynesian demand effects. Independent central bankers would manage macroeconomic demand with monetary policy, leaving governments to set taxes and spending plans to achieve political or supply-side objectives.

Worth a read.