Some good news: if one looks carefully at the numbers, while deficits and debt levels are high, they are manageable. They require an effort in the years (decades?) ahead but we have seen large fiscal consolidations in the past of a size which is similar to what is required from today's perspective. This seems to be the perspective of financial markets as interest rates on government bonds remain low and there is no obvious pricing of a default risk.
The arithmetics of fiscal discipline are simple and the future effort will depend on the difference between the interest rate that governments will face and the growth rate of their economy. In emerging markets, we have seen rapid changes in this difference (interest rate getting very high as growth rates slow down) leading to crisis as the burden becomes unmanageable. While this is not the scenario that one might expect for advanced economies, it all depends on the credibility that governments established. And theoretically one could imagine a self-fulfilling prophecy where a crisis starts with a small change in the perceived credibility of governments which increases interest rates and leads to unsustainable interest payments.
The bad news is that there is no guarantee that governments will behave better going forward. Yes, we know the effort that is needed to stabilize debt-to-GDP ratios but history is full of examples where once the crisis is over we forget about fiscal policy discipline. And here is where we need an exit strategy. It is not about about announcing a short-term schedule to remove the current fiscal stimulus is about giving reassurances that in the next decade or decades we will look at sustainability of government finances in a different way. I have argued in some of my academic research (together with my co-blogger Ilian Mihov) that there is a need to think about institutional reforms that change the way we think about fiscal policy and budgets. Other academics have presented similar proposals, all of them implying the creation of some constraints around the power of governments to decide on all aspects of fiscal policy. While numerical rules are the simplest way to think about constraints (budget balance rules, stability and growth pact), the empirical evidence is that implicit constraints - such as those created by the political process through which budgets are decided- can be as powerful and less rigid. A change in this direction would be a good "exit strategy" for governments. Without the need to harm the current recovery, it would provide the necessary foundations for a credible fiscal policy in the years ahead.