Controversy over labor force concepts arises to a large extent because of the varied and often-conflicting uses of the data. The Census Bureau has tried to meet this problem by providing detailed information on major categories and by experimental work to measure borderline groups. Types of questions that have been examined are: difference between labor force participation during a year and a calendar week; underemployment of employed persons; strength of job attachments of persons not at work for various reasons; the appropriate classification of persons on the fringe of the labor force. Efforts have been made also to reconcile statistics from households and from business and administrative records.