Furthermore, the vast international literature on economic and financial crises has identified many cases, with the causes and consequences of these episodes much debated (Kelly 2007, Reinhart and Rogoff 2009, Laeven and Valencia 2013). A primary lesson from the literature is that crises can emerge for many reasons.
While some busts indeed follow boom phases, it is also possible to experience a negative shock that pushes a normally-functioning economy into crisis conditions within a short time period. In addition, not all booms are followed by busts – the infamous “soft landing” scenario sometimes plays out.