The 2010 U.S. census has questions primarily about population, with one question about housing. Comprehensive and interdisciplinary works about the 2010 census will be classed as works about population, following the rule given in section 5.7 (B) of the Introduction: “Class a work on two subjects with the subject receiving fuller treatment.” The interdisciplinary number for population is 304.6 Population.
Works about data collection methods of the census are classed in 304.60723 Population—descriptive research (built with 304.6 Population plus T1—0723 Descriptive research). At T1—0723 Descriptive research are an including note and a class-here note:
Including case studies [formerly T1—0722]; sampling techniques; surveys, questionnaires, field work, observation, interviews
Class here data collection
At T1—0727 Statistical methods is the see reference: “For data collection, see T1—0723.” Examples of works classed in 304.60723 are Looking for the Last Percent: The Controversy over Census Undercount, Sampling and the Census: A Case against the Proposed Adjustments for Undercount, and Experimentation and Evaluation Plans for the 2010 Census: Interim Report. What about the geographic aspect, since all the examples focus on the U.S. census? In the table of preference at the start of Table 1, T1—07 Education, research, related topics (except T1—074, T1—075) appears above T1—093–T1—099 Treatment by specific continents, countries, localities; extraterrestrial worlds. A basic rule for standard subdivisions is found at the start of Table 1: “Do not add one standard subdivision to another standard subdivision unless specially instructed.”
At T1—072 Research is the class-elsewhere note: “Class results of research in 001–999 without adding notation T1—072 from Table 1.” For works with census results about population of a specific geographic area, the end of the number will vary depending on whether the work deals with a limited time period. An example of a work with U.S. census results in a limited time period is 1990 Census Snapshot for All U.S. Places. It is classed in 304.6097309049 Population—United States—1990–1999 (built with 304.6 Population plus T1—09 Geographic treatment plus T2—73 United States plus 09 Historical treatment from add table under T1—093–T1—099 Treatment by specific continents, countries, localities; extraterrestrial worlds plus 049 from T1—09049 1990–1999, following instructions at T1—093–T1—099). An example of a work with U.S. census results over a long time period is Population of States and Counties of the United States: 1790 to 1990: From the Twenty-One Decennial Censuses. It is classed in 304.60973021 Population—United States—statistics (built with 304.6 Population plus T1—09 Geographic treatment plus T2—73 United States plus 021 Statistics from add table under T1—093–T1—099, following instructions at T1—093–T1—099). At T1—093–T1—099 is the following note: “In the table above, observe preference as given at beginning of Table 1 . . . . .” In the table of preference at the beginning of Table 1, T1—0901–T1—0905 Historical periods appears above T1—021 Tabulated and related materials (the latter has the including note: “Including statistics, statistical graphs”); consequently, for works treating a limited time period, such as the results of a single census, notation for historical period is preferred over notation for statistics.