This thesis is devoted to the study of two of the most important macroeconomic events from recent times: the Great Recession of 2008-09, and Austerity in 2010-13.We argue that both phenomena have been primarily demand-driven, with the former taking the form of a synchronized self-fullling panic, and recessions in several advanced countries during the latter being driven by the increased desire of households to save due to cuts in welfare state spending.In Chapter 1, The Great Recession: Divide between Integrated and Less Integrated Countries (joint with Eric van Wincoop and Gang Zhang), we conrm previous evidence about the absence of a monotonic relationship between the decline in growth of countries during the Great Recession and their level of trade or nancial integration, but document instead a strong discontinuous relationship. Countries whose level of economic integration (trade and nance) was above a certain cuto saw a much larger drop in growth than less integrated countries, a nding that is robust to a wide variety of controls. We argue that standard models based on transmission of exogenous shocks across countries cannot explain these facts. Instead, we explain the evidence in the context of a multi-country model with business cycle panics that are endogenously coordinated across countries.In Chapter 2, A Welfare State-based Fiscal Multiplier , we argue that current new-Keynesian theory cannot explain empirical evidence of larger-than-normal scal multipliers during the 2010-13 period if the combination of countries committing to a sizable reduction of public debt and low output growth expectations led agents to believe that austerity measures were permanent. Instead, we explain the evidence in the context of a new-Keynesian model with incomplete markets and heterogeneous households, where the reduced level of public insurance implied by a permanent cut of welfare spending increases incentives to save for precautionary reasons, thus leading to a Paradox-of-Thrift type of recession. Consistent with this view, we nd empirically that the welfare state spending multiplier was signicantly larger than the non-welfare and tax multipliers for advanced countries engaging in scal adjustments over this time period.