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Suggested Citation:"A Basic Information on Census Questionnaires." National Research Council. 1995. Modernizing the U.S. Census. Washington, DC: The National Academies Press. doi: 10.17226/4805.
This appendix summarizes information on the content of the decennial censuses, 1960-1990. In general, the number of items for which data are obtained in the census and the major content areas have remained about the same over this period. The 1990 long-form questionnaire (which includes the short-form questions) is shown in Figure A.1 (although the dimensions of the census form have been altered to fit into this book, the content is the same as on the original form). All households received the short form; a sample of households received the long form. The short form is the first 7 pages and page 32 of Figure A.1. The actual short form delivered to households in 1990 was 4 pages. The appendix also provides information on the number of households receiving and responding to the questionnaires in the 1970-1990 censuses.
Table A.1 is a summary of total population and housing items asked in the short-and long-form questionnaires. The summary shows great stability in the number of short-form population items, which are limited to basic demographic information. There has been a decline in the number of short-form housing items; hence, the burden of the short form on the population has declined somewhat over time. The number of long-form items (population and housing combined) grew from 49 items in 1960 to 64 items in 1970 and 65 items in 1980, declining to 58 items in 1990 (the Office of Management and Budget played a role in this reduction—see Chapter 6). In the 1970 census, the use of matrix
Suggested Citation:"A Basic Information on Census Questionnaires." National Research Council. 1995. Modernizing the U.S. Census. Washington, DC: The National Academies Press. doi: 10.17226/4805.
sampling reduced the burden of the long form on individual households (the 1960 census also used matrix sampling but to a more limited extent).
The table indicates that the burden of the long form has progressively declined in terms of the sampling rate. Twenty-five percent of households were designated to receive the long form in 1960, 20 percent in 1970, 19 percent on average in 1980, and 16 percent on average in 1990. The 1970 census used a type of matrix sampling for both population and housing items: 15 percent of households received a markedly shorter long form, and 5 percent received a longer long form; some items were common to both forms, producing a 20 percent sample for those items.
The 1960 census also employed matrix sampling but to a more limited extent from the perspective of responding households. Different forms were used in large cities of 50,000 or more population and other areas; each contained a couple of questions unique to the form. In addition, in conventionally enumerated areas in 1960 (see below), 20 percent of households were asked one set of housing items by enumerators, and 5 percent were asked another set; some items were asked in common, producing a 25 percent sample for those items. In the remaining areas, however, which covered about 80 percent of households, every household in the 25 percent sample was asked to fill out and mail back a long form with all of the sample questions for the type of place (large city or other). Enumerators then transcribed the answers to computer-readable forms, transcribing the answers for 25, 20, or 5 percent of households, depending on the item (see Table A.2).
Table A.2 lists the various detailed items on the census. The housing portion of the long-form questionnaire no longer includes such items as possession of a washing machine or other appliances. The population portion of the long-form questionnaire, over time, has included more questions on disability and ancestry (although the question on birthplace of parents was deleted after 1970) and fewer on marriage and schooling. The greatest number of questions are related to employment, occupation, and income. For the income question, each added income source (e.g., pensions) is counted as a separate item because the respondent must consciously disaggregate the preceding year's income into component parts
Table A.3 lists the total number of both vacant and occupied housing units and the number of occupied housing units (households) in 1970, 1980, and 1990. Total housing units have increased over time from 69 million in 1970 to 102 million in 1990; total households have increased from 64 million to 92 million over the same period. Also shown are the number of households receiving the short and long forms and, for each form type, the number receiving and returning
Suggested Citation:"A Basic Information on Census Questionnaires." National Research Council. 1995. Modernizing the U.S. Census. Washington, DC: The National Academies Press. doi: 10.17226/4805.
a form by mail. (Other households were visited by an enumerator to pick up their form.)
Assessing changes over time in the willingness of households to cooperate with the census, specifically, their willingness to mail back a form, is difficult because of changes in methodology. 1 The 1960 census was an exploratory attempt at mailback questionnaires and was limited to the long form (for this reason, Table A.3 does not include figures for 1960). The U.S. Postal Service (USPS) delivered unaddressed short forms for households to fill out and wait for enumerator pick-up. At the time of pick-up in areas of the country containing about 80 percent of the housing, enumerators left long forms at every fourth unit (25%) to be completed and returned by mail. (This was termed the two-stage procedure.) In the remaining areas, enumerators obtained answers to the long-form items from every fourth unit at the same time as they picked up the short form. (This was termed the single-stage or conventional procedure.)
In 1970, the USPS delivered questionnaires to addresses on a mailing list developed by the Census Bureau for areas containing about 60 percent of the housing. Four-fifths of housing units received a short form and the other one-fifth received one of two versions of the long form. In these mailout/mailback census areas, about 87 percent of households (occupied housing units) returned a questionnaire. The mail return rate (based on occupied housing units) was 87.8 percent for the short form and 85.5 percent for the long form, a difference of 2.3 percentage points. In the remaining conventionally enumerated areas containing about 40 percent of the housing, households received an unaddressed short form and were then visited by an enumerator who picked up the short form and, at every fifth household (20%), administered one of two versions of the long form.
In 1980, the mailout/mailback census areas covered about 96 percent of the housing. Overall, about 19 percent of housing units received the long form. In places with an estimated population of less than 2,500, the sampling rate was 1 in 2 (50%). In all other areas, it was 1 in 6 (17%). In the mailout/mailback areas, about 81 percent of households mailed back their questionnaire. The mail return rate (based on occupied housing units) was 81.6 percent for the short form and 80.1 percent for the long form, a difference of 1.5 percentage points.
In 1990, the mailout/mailback areas covered about 95 percent of the housing. (In most of these areas, the USPS delivered the questionnaires, but, in some areas, census enumerators made the delivery—see Appendix B.) Overall, about 17 percent of the housing units received a long form. In places (such as counties and incorporated places) with an estimated 1988 population of less than 2,500, the sampling rate was 1 in 2 (50%). Based also on precensus estimates, very populous census tracts (or equivalents) had a sampling rate of 1 in 8 (12.5%). All other areas had a sampling rate of 1 in 6 (17%). In the mailout/mailback areas, 74 percent of households returned their questionnaires. For both long and short forms, mail return rates (based on occupied housing units) were lower for
Suggested Citation:"A Basic Information on Census Questionnaires." National Research Council. 1995. Modernizing the U.S. Census. Washington, DC: The National Academies Press. doi: 10.17226/4805.
