Recently, Institute of State Governance Studies and the Co-Innovation Center for State Governance of Peking University published their latest research- Political Bubble - Policy Deviation and Transactional Democracy in the European Debt Crisis . The book takes the European debt crisis as the analysis object, and uses political-economic interactive analysis methods to conduct in-depth analysis and study on the policy causes, political roots, and deficiencies of the Western transactional democratic system in the perspective of policy deviation. The unsustainability of the government debt of the European debt crisis countries is the result of the combined effect of the continuous expansion of public expenditures and the extreme shortage of fiscal revenue in these countries. Factors that contribute to the expansion of public expenditure include the large scale of the public sector, generous welfare policies, and an aging population and high unemployment rate. Generous welfare policies are only possible rather than inevitable factors that trigger the sovereign debt crisis. Compared with the expansion of public spending, the shortage of fiscal revenue is a more fundamental factor that leads to distorted accumulation of government debt and lack of sustainability. The source of fiscal revenue shortage in crisis countries lies in the weak economic competitiveness and the resultant economic faults. The weak economic competitiveness is caused by a series of liberal economic policies. Through cross-national comparative analysis, the book finds that the European debt crisis was not caused solely by generous welfare policies, nor was it simply caused by laissez-faire attitude and the related economic breakdown, but the long-term improper combination of the two types of policies. As a result, this long-term policy deviation is the real cause of the European debt crisis, and the creation and maintenance of policy deviations are rooted in the transactional democracy system of crisis countries. Western democracies are deviating from their original intentions and being transformed into transactional democracy under the control of the elite. This type of democracy faces deep crisis and severe challenges and its long-term policy deviations are precisely the political bubbles behind the economic bubbles of the sovereign debt crisis.