"The usefulness and importance of a system of national accounts can most readily be appreciated by returning to origins of the method and at the same time considering the actual necessity of this type of analysis. This new analytical technique was first introduced in Great Britain during the Second War. John Maynard Keynes was at that time an expert adviser to the Treasury on problems of war finance, and his assistants included Richard Stone. Keynes took as his starting point a balance between total current resources (including real gross national product) on the supply side and total consumption, investments and expenditure for the war effort on the demand side. Richard Stone's experiments in the systematic processing of the copious flood of statistical material in the form of national accounts moved Keynes to exclaim: "We are in a new era of joy through statistics". Stone's ideas on the design of national accounts were from the beginning aimed at full integration of national accounts for the various sub-sectors which between them represented the entire national management of resources. Every item of income and expenditure on one side of an account must recur as the opposite item - expenditure and income respectively - in another account. An integral system of accounts included, for example, household income and expenditure, the expenditure and revenues of the enterprise sector (expenditure, for example, including wage payments), national saving and investment, public sector spending and revenues and, finally, balances of payments vis-à-vis other countries. This double-entry accounting provided opportunities of cross-checking statistics for the numerous transactions. Figures from different sources had to tally."