Since 2007, a crisis relating to subprime mortgage lending, which originated in the United States, has escalated into a general global financial crisis. World economic growth has suffered a heavy blow, pushing some countries to the verge of bankruptcy. This widespread, large-scale and highly destructive financial crisis has caused economists to revisit, and sometimes question, existing theories. At the same time, policy makers from various countries have had to develop new economic policies and responses on the fly in an attempt to avoid the worst-case scenarios.