(I) Writing in the 1930s, J.M. Keynes was mainly concerned with unemployment. (II) For him, the question was why it persisted. (III) Since 1945 the twin objectives of economic growth and full employment have been the primary concern of developed countries throughout the world. (IV) His own answer to this was that employment was determined by the level of output, and this was determined by demand. (V) Therefore, the level of employment could be regulated by managing the level of demand.