By a ‘spontaneous disturbance' we shall mean any change in the underlying conditions, the cause of which we are prepared to take for granted and do not wish to examine, but the effect of which on the domestic and external position of our two countries we wish to examine. By a ‘policy' change we shall mean a change which the State or some public authority brings about as a result of a definite decision of State policy in order to achieve some given end of general economic policy and in particular to offset some of the effects of a ‘spontaneous disturbance'. Finally, by an ‘induced' change is meant a change in some quantity which occurs on purely commercial principles because of the repercussions of some previous ‘spontaneous' or ‘policy' change.