Numerous crises have occurred since the beginnings of the modern economic system, from the Dutch Tulip Mania of 1636 and the South Sea Bubble of 1720 to the Dollar Crisis and Asian Financial Crisis. Scholars have written about the causes and remedies of financial crisis, resulting in a substantial amount of literature on the subject especially after the Great Depression. The writing on financial crisis declined between the end of World War II and the monetary crises in the early 1970s, but has become vibrant again since the 1980s. Some of the earliest voices that contributed to the intellectual history of studying financial crisis include Adam Smith, Karl Marx, David Ricardo, Walter Bagehot, and John Maynard Keynes. These men provided the foundation for understanding the central issues and questions about financial crisis and influenced the debates and scholarship that followed. One such debate involved monetarists vs. business cycle theorists. The monetarists argue that crises are caused by changes in the money supply, while those favoring a business cycle approach insist that expansions and contractions are part of economic interactions and so the economy will at times experience crises. As crises continue to affect both domestic and global financial markets, more perspectives are added to the discussion, including those that invoke rational expectations and economic models, along with those that draw from international political economy. There are also questions that remain unanswered, such as the issue of crisis response and that of financial fragility.