Each year (between 1956 and 1965) data were collected from the men’s companies (e.g., interviews with departmental colleagues, supervisors, former bosses), as well as from the men themselves (e.g., interviews with questionnaires of attitudes and expectations) to determine their progress. No information about any man’s performance during assessment was ever given to company officials. There was no contamination of subsequent criterion data by the assessment results, and staff evaluations had had no influence on the careers of the men being studied.