A second source of shock is a supply shock, an example of which would be a one-time, permanent increase in oil prices. We have had several examples of very sharp increases in oil prices, especially in the 1970s, and, more recently, oil prices have been declining since the end of 1996.
When there is a sharp rise in oil prices, there will be a temporary burst of inflation. In addition, an adverse supply shock will typically result in a decline in aggregate demand and hence in output and employment.