Standards of Measurement
In measuring national income and gross national product it is usual to restrict coverage in the main to the production of goods and services for sale. Thus the national income does not include any allowance for the output or production of housewives or of home gardening. The exclusion of some such forms of production is occasionally criticised by professional economists. For instance, in certain underdeveloped countries a substantial amount of subsistence farming exists, and some kind of assessment of the value of production for the producer's own use is therefore necessary. Such measurement raises many serious problems. In New Zealand allowance is made for one kind of income which does not take the form of a money flow. The item is provisional for the rental value of owner-occupied houses.
The total value of production can also be described in terms of the final use made of produced goods and services. The measure of total use made of goods and services produced is gross national expenditure and equals gross national product. This total includes measures of personal and Government consumption, capital formation, and changes in stocks held. An adjustment is also made for the difference between the total value of goods and services exported and of goods and services imported. This difference is known as net investment overseas.
An official estimation of national income is comparatively recent, and it is only since the 1939–45 War that international standards of measurement have been developed. From its inception the United Nations Statistical Office has played a central part in the development and formulation of national accounting procedures, and these are now followed in large part in most non-communist countries.