From the 18th through the middle of the 20th century, enumerators traveled from house to house to take the census. The enumerators filled in information on a census schedule for members of the household. A uniform printed population schedule was first developed and used for the 1830 census. Separate schedules were eventually used to collect information on manufacturing, commerce, mining and other economic activities.
For the 1960 census, the Census Bureau mailed out questionnaires to households in urban areas. Householders were asked to complete the questionnaire and hold it until an enumerator came by to pick it up. In 1970, the Census Bureau implemented a mail-out/mail-back enumeration for households in larger metropolitan areas (approximately 60 percent the U.S. population). Today, mail-out/mail-back procedures are used extensively for both the census and surveys. Self-enumeration by mail improves quality of the resulting data and reduces costs.
In the 1990s, the Census Bureau developed electronic data collection methods. New interviewing techniques, including computer-assisted personal interviewing (CAPI) and computer-assisted telephone interviewing (CATI), complemented mail-out/mail-back procedures and helped cut costs. Electronic reporting, employing computer tape, diskettes, e-mail, and electronic questionnaires, made it easier for businesses to respond to economic surveys and censuses.