As a key regional sovereign currency in the process of European integration, the euro's institutional design combines a unified monetary policy with a decentralized fiscal policy. However, the 2008 financial crisis, the COVID-19, the Russia-Ukraine conflict and other multiple crises had a serious impact on the euro area economy, exposing the inadequacy of the system design. Faced with challenges, European integration has shown resilience by responding to crises through institutional reforms and filling institutional gaps. The establishment of the euro is a bold experiment in international monetary cooperation, which has reference significance for monetary cooperation in East Asia and the future construction of the "Asian dollar". This article will use the theory of optimal currency areas to analyze the major crises encountered by the eurozone, explore the role of asymmetric shocks in promoting institutional innovation, reveal the shortcomings of macroeconomic governance structures, and predict the direction of future institutional innovation.

1、 The Theory of Optimal Currency Area and the Research Design of This Paper

The Optimal Currency Area (OCA) theory originated in the 1960s, aiming to explore the costs and benefits of redefining currency boundaries and provide a new perspective for international monetary cooperation. The OCA theory emphasizes the comparison of the advantages and disadvantages of fixed exchange rates and floating exchange rates, and believes that the optimal currency area should have adjustment measures such as labor mobility and fiscal integration to reduce the negative impact of asymmetric shocks. The establishment of the Eurozone is based on the OCA theory, where countries abandon their own currencies to form a unified currency area, facing the challenge of asymmetric shocks. This study selects the asymmetric shocks such as the European debt crisis, the COVID-19 epidemic and the Russia-Ukraine conflict as the objects of study, analyzes their impact on the institutional reform of the euro area, and discusses the basic laws of integrated institutional reform and the overall trend of macroeconomic governance reform.

2、 Asymmetric impact that triggered the European debt crisis

The European debt crisis is the first serious crisis faced by the euro, with complex causes including institutional and structural roots, as well as a chain reaction of sudden crises. The formation of a crisis is related to factors such as differences in the development level and economic structure of member countries, the differentiation effect under a unified monetary policy framework, and the sudden halt of capital flows. The unified currency led to the convergence of interest rates in member countries, which led to debt driven growth and foam type economic prosperity, especially in southern Europe. The unified monetary policy in the eurozone has exacerbated structural differences in macroeconomic conditions among member states, leading to a mismatch between real interest rates and real exchange rates. The 2008 financial crisis led to a sudden halt in capital flows, unsustainable growth models in peripheral countries, and a sharp increase in public debt. The lack of rescue mechanisms in the design of the eurozone system has led to the predicament of peripheral countries. The principle of fiscal separation has led to speculation in sovereign bonds in the market, increased the risk of debt default in peripheral countries, price differentiation in the public bond market, and new asymmetric shocks experienced by peripheral countries.

3、 Reform measures to enhance institutional resilience in the eurozone

The European debt crisis exposed the misconceptions of the eurozone under the conditions of international monetary cooperation and economic financialization, leading to inadequate response to macroeconomic imbalances and asymmetric shocks within the region. To enhance institutional resilience, the EU has implemented multiple reform measures: firstly, strengthening macroeconomic governance, including implementing the "European semester" system, reforming the Stability and Growth Pact, and introducing procedures for excessive imbalances; The second is to establish a banking alliance, including a single regulatory mechanism, a single clearing mechanism, and a unified bank deposit insurance; Thirdly, establish a permanent rescue mechanism for the eurozone, such as the European Financial Stability Mechanism and the European Stability Mechanism; Fourthly, the European Central Bank directly intervenes in the sovereign debt market during crises, acting as the lender of last resort for member governments and stabilizing the market through securities market programs and direct currency trading programs. These measures aim to prevent new macroeconomic imbalances, address potential asymmetric shocks, and maintain financial stability in the eurozone.

4、 New crises and progress in fiscal integration

After the European debt crisis, although the Eurozone economy has stabilized, public debt remains high and economic growth is fragile and uneven. The COVID-19 and the Russia-Ukraine conflict pose a serious challenge to the economic and monetary union. The COVID-19 epidemic has led to pressure on the medical system of EU countries, sharp decrease in fiscal revenue, increase in expenditure, and financial pressure on the government. In response to the epidemic, the European Union has adopted an expansionary monetary policy and an active fiscal policy. The European Central Bank has launched the "Pandemic Emergency Bond Purchase Plan", and EU leaders have reached an agreement on a large-scale economic recovery plan, launching the "Next Generation EU" plan, borrowing in the form of EU common debt, responding to economic shocks through union deficits, promoting common finance, and enhancing the resilience of the monetary union system. The conflict between Russia-Ukraine conflict has made the European economy worse. Energy prices fluctuate, inflation intensifies, macroeconomic indicators decline, trade accounts with Russia deteriorate, and consumption and production suffer. The spillover effect of conflicts has squeezed the fiscal space of European monetary policy and increased fiscal pressure. The EU needs to invest financial resources to respond, provide assistance, increase military spending, and put pressure on financial resources. The Ukrainian crisis has had an asymmetric impact on the eurozone, with Eastern European countries facing higher military spending pressure than Western European countries. Many countries need to choose between welfare and military spending, and Germany has issued additional debt to respond. Eurozone member states advocate for joint defense financing, but have been boycotted.

5、 Comprehensive evaluation of institutional reforms in the Eurozone

Discussed the dilemma of the governance structure of the eurozone, namely the "three incompatibility" issue, including non revocable membership, monetary orthodoxy, and fiscal orthodoxy. Under systemic shocks, these pillars cannot be preserved simultaneously, leading to the need to relax compliance with the monetary and fiscal policy taboos stipulated in EU treaties. The chapter emphasizes the necessity and urgency of reforming the eurozone system, pointing out that only by exceeding treaty provisions can the goal of preserving the integrity of the eurozone be achieved. The article analyzes the impact of financial shocks on the eurozone and points out that the liberalization of the financial sector and the negative externalities it generates are the real threats to the eurozone sovereign debt crisis. At the same time, the key role of the European Central Bank in maintaining financial stability was emphasized, including providing liquidity, preventing financial market fragmentation, and reducing government debt burden. In addition, the chapter also discusses the inevitable trend of fiscal integration in the eurozone, pointing out that after experiencing multiple crises, the monetary policy space and fiscal operational capacity of the eurozone have been extremely overdrawn, and heavily indebted countries have less room for fiscal maneuvering. They must rely on the unconventional monetary policy of the European Central Bank to prevent debt collapse. Finally, the article proposes that in order to enhance the economic competitiveness of eurozone countries and achieve green and digital transformation, significant investment is needed, and issuing bonds through collective credit is the only way to achieve this goal.