Childspacing (Volume II, Part III - Subject Reports)
Collection and Processing of Data
Several enumeration forms were used to collect the information for the 1960 Census of Population. A few days before the census date, the Post Office Department delivered an Advance Census Report (ACR) to households on postal delivery routes. This form contained questions which were to be answered for every person and every housing unit. Household members were requested to fill the ACR and have it ready for the enumerator. The census enumerator recorded this information on a form specially designed for electronic data processing by FOSDIC (Film Optical Sensing Device for Input to Computer). The information was either transcribed from the ACR to the complete-count FOSDIC schedule or entered on this schedule during direct Interview.
Additional questions on social, demographic, and economic characteristics were asked at one-fourth of the households. In the densely populated areas, the enumerator left a Household Questionnaire to be completed by all occupants of these sample housing units. The completed questionnaire was mailed to the local census office and the information was transcribed from the Household Questionnaire to a sample FOSDIC schedule. When the Household Questionnaire was not returned or was returned without having been completed, the enumerator collected the missing information by personal visit or by telephone and entered it directly on the sample FOSDIC schedule. In the remaining areas, when the enumerator picked up the ACR, he obtained all the information by direct interview and recorded it directly on the sample FOSDIC schedule.
Soon after the enumerator started work, his schedules were examined in a formal field review. This operation was designed to assure at an early stage of the work that the enumerator was performing his duties properly and had corrected any errors he had made.
More detailed descriptions of the 1960 Census procedures in the collection and processing of the data are given in reports entitled United States Censuses of Population and Housing, 1960: Principal Data Collection Forms and Procedures, 1961; and Processing the Data, 1962, U.S. Government Printing Office, Washington, D.C. 20402.
Manual Editing and Coding
After the FOSDIC forms had been checked for completeness in the field, they were sent to a central processing office for Manual Electronic Processing and Coding and for microfilming. Except where some special problems arose, there was no manual coding of the FOSDIC forms for complete-count data. On the sample forms, the manual operation was limited to those items where coding required the reading of written entries and therefore could not be done effectively by machine. The coding clerks converted the written entries to codes by marking the appropriate circles on the FOSDIC schedules and at the same time were able to correct obviously wrong entries and sometimes supply missing information.
After the enumerators and coders recorded the information by marking the appropriate circles, the schedules were microfilmed. The information on the microfilm was then read by FOSDIC, which converted the markings to signals on magnetic tape. The taps, in turn, was processed in an electronic computer, which was used extensively to edit and tabulate the data and to produce the publication tables.
For a majority of items, nonresponses and inconsistencies were eliminated by using the computer to assign entries and correct inconsistencies. In general, few assignments or corrections were required, although the amount varied by subject and by enumerator.
The assignment of an acceptable entry by machine was based on related information reported for the person or on information reported for a similar person in the immediate neighborhood. For example, in the assignment of age in the complete-count tabulations, the computer stored reported ages of persons by sex, color or race, household relationship, and marital status; each stored age was retained in the computer only until a succeeding person having the same characteristics and having age reported was processed through the computer; this stored age was assigned to the next person whose age was unknown and who otherwise had the same characteristics. This procedure insured that the distribution of ages assigned by the computer for persons of a given set of characteristics would correspond closely to the reported age distribution of such persons as obtained in the current census.
The extent of the allocations for nonresponse or for inconsistency is shown for the United States and for States, places of 10,000 inhabitants or more, and other areas in appendix tables in chapters B, C, and D of 1960 Census of Population, Volume I, Characteristics of the Population. To simplify the processing procedures, records for women in groups (2) and (3) were purposely deleted if they indicated that the woman had even one child present who was born before the women was 14 years old, that the woman was married before age 14, 3 or that the woman had an improbably large number of children ever born for her age. It was expected that about one percent of the records for groups (2) and (3) would be deleted for the reasons just stated. But, through programming errors, additional records were inadvertently deleted, and this situation was not discovered until all tabulations had been made. The magnitude of the deletions (from all sources combined) can be determined from table B.
Human and mechanical errors occur in any mass statistical operation such as a decennial census. Such errors include failure to obtain required information from respondents, obtaining Inconsistent information, recording Information in the wrong place or incorrectly, or otherwise producing inconsistencies between entries on interrelated items on the field documents. Sampling biases occur because some of the enumerators fall to follow the sampling instructions. Clerical coding and Electronic Processing errors occur, as well as errors in the Electronic Processing operation.
Careful efforts are made in every census to keep the errors in each step at an acceptably low level. Review of the enumerator's work, verification of manual coding and Electronic Processing, checking of tabulated figures, and Ratio Estimation of sample data to control totals from the complete count reduce the effects of the errors in the census data.
In a few instances, this report shows numbers of women that vary from table to table by relatively small amounts. For example, table 3 shows 18,700,334 white single women age to 17 for the 5-year period 1955 to 1959. The data by single calendar years in table 1 for the same 5-year period yield a total of 18,718,691 women. Although the difference of 18,357 seems large as an absolute number, it is a relatively small proportion of the total number of women to 17 years old. Differences of this type came from variations between the tabulation procedures used in preparing different tables in the report. Table 3 was tallied by an iterative (loop) procedure for single women which (logically) was to conclude with the calendar year in which the woman first married but which actually permitted a slight overcount of single women.
Tables 19 and 24 illustrate other differences between tables. The tables present data for identical cohorts of women for the United States, but table 24 shows about one percent more cumulated births at successive ages than does table 19. These discrepancies arose because of minor differences in the procedures used for tabulating births. For example, in table 19 half of the births that occurred in the calendar quarter in which a woman reached the midpoint of the age were tabulated as occurring before the midpoint of the age and half were tabulated as occurring after the midpoint. In table 24, all such births were counted as occurring before the midpoint of an age.
Some innovations in the 1960 Censuses reduced errors in processing and others produced a more consistent quality of Electronic Processing. The elimination of the card-punching operation removed one important source of error. The extensive use of electronic equipment insured a more uniform and more flexible edit than could have been accomplished manually or by less intricate mechanical equipment. It is believed that the use of electronic equipment in the 1960 Censuses has improved the quality of the Electronic Processing compared with that of earlier censuses but, at the same time, it has introduced an element of difference in the statistics.
Evaluative material on accuracy of some of the population characteristics used in this report can be found in Evaluation and Research Program of the U.S. Censuses of Population and Housing. 1960, report numbers 5, and 6. A report entitled The Post-Enumeration Survey: 1950; Technical Paper No. 4, presents evaluative material on the 1950 Census.