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Sample characteristics: United States

Census/survey characteristics
Type Census
Title United States Census of 1850
Statistical agency Department of the Interior
Population universe All persons living in the United States including temporarily absent residents
De jure or de facto De jure
Census/survey day June 1, 1850
Field work period June 1, 1850
Questionnaire The census operation involved six forms. Form 1 was used to enumerate free persons and collected information on individual characteristics. Form 2 was used to enumerate slaves. Other forms were used to record information about agriculture and industry.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design Not applicable
Sample fraction 100%
Sample size (person records) 19,987,946
Sample weights Not applicable
Units identified in microdata
Dwellings No
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings A separate inhabited tenement, containing one or more families under one roof. Where several tenements are in one block, with walls either of brick or wood to divide them, having separate entrances, they are each to be numbered as separate houses; but where not so divided, they are to be numbered as one house. 
Households One person living separately in a house, or a part of a house, and providing for him or herself, or several persons living together in a house, or in part of a house, upon one common means of support, and separately from others in similar circumstances
Census/survey characteristics
Type Census
Title United States Census of 1850
Statistical agency Department of the Interior
Population universe All persons living in the United States including temporarily absent residents
De jure or de facto De jure
Census/survey day June 1, 1850
Field work period June 1, 1850
Questionnaire The census operation involved six forms. Form 1 was used to enumerate free persons and collected information on individual characteristics. Form 2 was used to enumerate slaves. Other forms were used to record information about agriculture and industry.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design 1-in-100 national random sample of the free population. African-American slaves are not included in this dataset. Individual-level data on the 1850 slave population is available at the
Sample fraction 1%
Sample size (person records) 197,796
Sample weights Self-weighting (expansion factor=100)
Units identified in microdata
Dwellings No
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings A separate inhabited tenement, containing one or more families under one roof. Where several tenements are in one block, with walls either of brick or wood to divide them, having separate entrances, they are each to be numbered as separate houses; but where not so divided, they are to be numbered as one house. 
Households One person living separately in a house, or a part of a house, and providing for him or herself, or several persons living together in a house, or in part of a house, upon one common means of support, and separately from others in similar circumstances
Census/survey characteristics
Type Census
Title United States Census of 1860
Statistical agency Department of the Interior
Population universe All persons living in the United States including temporarily absent residents and sailors at sea, no matter how long they may have been absent, if they were believed to be still alive. "Indians not taxed", which refers to Native Americans living on reservations or under tribal rule. Native Americans who had renounced tribal rule and "exercise the rights of citizens" were to be enumerated.
De jure or de facto De jure
Census/survey day June 1, 1860
Field work period June 1, 1860
Questionnaire The census operation involved six forms. Form 1 was used to enumerate free persons and collected information on individual characteristics. Form 2 was used to enumerate slaves. Other forms were used to record information about agriculture and industry.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design 1-in-100 national random sample of the free population. African-American slaves are not included in this dataset. Individual-level data on the 1860 slave population is available at the
Sample fraction 1%
Sample size (person records) 273,596
Sample weights Self-weighting (expansion factor=100)
Units identified in microdata
Dwellings No
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings A separate inhabited tenement, containing one or more families under one roof. Where several tenements are in one block, with walls either of brick or wood to divide them, having separate entrances, they are each to be numbered as separate houses; but where not so divided, they are to be numbered as one house. 
Households One person living separately in a house, or a part of a house, and providing for him or herself, or several persons living together in a house, or in part of a house, upon one common means of support, and separately from others in similar circumstances
Census/survey characteristics
Type Census
Title United States Census of 1870
Statistical agency Department of the Interior
Population universe All persons living in the United States including temporarily absent residents and sailors at sea, no matter how long they may have been absent, if they were believed to be still alive. "Indians not taxed", which refers to Native Americans living on reservations or under tribal rule. Native Americans who had renounced tribal rule and "exercise the rights of citizens" were to be enumerated.
De jure or de facto De jure
Census/survey day June 1, 1870
Field work period June 1, 1870
Questionnaire The census operation involved four schedules. Schedule 1 was used to enumerate households and collected information on individual characteristics.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design 1-in-100 national random sample of the population
Sample fraction 1%
Sample size (person records) 383,358
Sample weights Self-weighting (expansion factor=100)
Units identified in microdata
Dwellings No
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings A house standing alone, or separated by walls from other houses in a block. Hotels, poorhouses, garrisons, asylums, jails, and similar establishments, where the inmates live habitually under a single roof, were considered single dwelling houses for the purposes of the census.
Households One or more persons living together and provided for in common. A single person, living alone in a distinct part of a house, may constitute a family; while, on the other hand, all the inmates of a boarding house or a hotel will constitute but a single family, though there may be among them many husbands with wives and children. Under whatever circumstances, and in whatever numbers, people live together under one roof, and are provided for at a common table are considered a family.
Census/survey characteristics
Type Census
Title United States Census of 1880
Statistical agency Department of the Interior
Population universe All persons living in the United States except for "Indians not taxed", which refers to Native Americans living on reservations or under tribal rule. Native Americans who had renounced tribal rule and "exercise the rights of citizens" were to be enumerated. Soldiers and civilian employees of the United States Army were included in the enumeration.
De jure or de facto De jure
Census/survey day June 1, 1880
Field work period June 1, 1880
Questionnaire The census operation involved five schedules. Schedule 1 was used to enumerate the population and collected information on individual characteristics. Other schedules were used to record information about agriculture, manufacturing, and to report social and mortality statistics.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design Not applicable
Sample fraction 100%
Sample size (person records) 50,140,482
Sample weights Not applicable
Units identified in microdata
Dwellings No
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings Any building or place of abode, of whatever character, material or structure, in which any person is at the time living, whether in a room above a warehouse or factory, a loft above a stable or a wigwam on the outskirts of a settlement, equally with a dwelling house in the usual, ordinary sense of that term. 
Households Persons living alone, families in the ordinary sense of the term, and also all larger aggregations of people having only the tie of a common roof and table. A hotel, with all its inmates, constitutes but one family. A hospital, a prison, an asylum is equally a family for the purposes of the census. On the other hand, the solitary inmate of a cabin, a loft, or a room finished off above a store constitutes a family. In the case of tenement houses and of the so-called "fiats" of the great cities, as many families are to be recorded as there are separate tables.
Census/survey characteristics
Type Census
Title United States Census of 1880
Statistical agency Department of the Interior
Population universe All persons living in the United States except for "Indians not taxed", which refers to Native Americans living on reservationsor under tribal rule. Native Americans who had renounced tribal rule and "exercise the rights of citizens" were to be enumerated. Soldiers and civilian employees of the United States Army were included in the enumeration.
De jure or de facto De jure
Census/survey day June 1, 1880
Field work period June 1, 1880
Questionnaire The census operation involved five schedules. Schedule 1 was used to enumerate the population and collected information on individual characteristics. Other schedules were used to record information about agriculture, manufacturing, and to report social and mortality statistics.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design 1-in-10 national random sample of the population with a 1-in-5 minority oversample. "Minorities" are defined as persons whose race was Native American or African American, whose race or birthplace indicated that they were Chinese, or whose name or birthplace indicated Hispanic origins. Households including a minority were sampled at a 1-in-5 rate.
Sample fraction 10%
Sample size (person records) 5,882,038
Sample weights Weights computed by data producer should be used for most types of analysis.
Units identified in microdata
Dwellings Yes
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings Any building or place of abode, of whatever character, material or structure, in which any person is at the time living, whether in a room above a warehouse or factory, a loft above a stable or a wigwam on the outskirts of a settlement, equally with a dwelling house in the usual, ordinary sense of that term. 
Households Persons living alone, families in the ordinary sense of the term, and also all larger aggregations of people having only the tie of a common roof and table. A hotel, with all its inmates, constitutes but one family. A hospital, a prison, an asylum is equally a family for the purposes of the census. On the other hand, the solitary inmate of a cabin, a loft, or a room finished off above a store constitutes a family. In the case of tenement houses and of the so-called "fiats" of the great cities, as many families are to be recorded as there are separate tables.
Census/survey characteristics
Type Census
Title United States Census of 1900
Statistical agency Department of the Interior
Population universe All persons living in the United States including temporarily absent residents and sailors at sea. Native Americans living on reservations or under tribal rule were enumerated using a separate schedule.
De jure or de facto De jure
Census/survey day June 1, 1900
Field work period June 1, 1900
Questionnaire The census operation involved four schedules. Schedule 1 was used to enumerate households and collected information on individual characteristics. Other schedules were used to enumerate the Native American population, and record information on agriculture and livestock.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design 1-in-20 national random sample of the population. Alaska and Hawaii are not included in this dataset.
Sample fraction 5%
Sample size (person records) 3,852,852
Sample weights Self-weighting (expansion factor=20)
Units identified in microdata
Dwellings Yes
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings A place in which, at the time of the census, one or more persons regularly sleep. It may be a room in a factory, store or office building, a loft over a stable, a canal boat, tent, or a wigwam. A building like a tenement or apartment house, if it has only one front door, counts as only one dwelling house, no matter how many persons or families live in it. But one building with a partition wall through it and a front door for each of the two parts, counts as two dwelling houses. So in a block of houses there are as many dwelling-houses as front doors. 
Households A group of individuals who occupy jointly a dwelling place or part of a dwelling place. A person who boards in one place and lodges in another should be returned as a member of the family where he lodges. A domestic servant, unless she sleeps elsewhere, is to be returned as a member of the family in which she works. All the occupants and employees of a hotel, if they regularly sleep there, make up, for census purposes, a single family, because they occupy one dwelling place. The same is true of all officials and inmates of an institution who live in the institution building. But where officers or employees of an institution sleep in detached houses or separate dwelling places, they are separate families.
Census/survey characteristics
Type Census
Title United States Census of 1910
Statistical agency Department of Commerce and Labor, Bureau of the Census
Population universe All persons living in the United States. Native Americans living on reservations or under tribal rule were enumerated using a separate schedule.
De jure or de facto De jure
Census/survey day April 15, 1910
Field work period April 15, 1910
Questionnaire The census operation involved six schedules. Schdule 1 was used to enumerate the population and collected information on individual characteristics. Other schedules were used to enumerate the Native American population, and record information on agriculture and livestock.
Type of fieldwork Direct enumeration
Microdata sample characteristics
Sample design 1-in-100 national random sample of the population, including Alaskans, Hawaiians, and persons enumerated on the American Indians schedules.
Sample fraction 1%
Sample size (person records) 923,153
Sample weights Self-weighting (expansion factor=100)
Units identified in microdata
Dwellings No
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography County
Unit definitions
Dwellings A place in which, at the time of the census, one or more persons regularly sleep. It may be a room in a factory, store or office building, a loft over a stable, a canal boat, tent, or a wigwam. A building like a tenement or apartment house, if it has only one front door, counts as only one dwelling house, no matter how many persons or families live in it. But one building with a partition wall through it and a front door for each of the two parts, counts as two dwelling houses. So in a block of houses there are as many dwelling-houses as front doors. 
Households A group of persons living together in the same dwelling place. The persons constituting this group may or may not be related by ties of kinship, but if they live together forming one household they should be considered as one family. Thus a servant who sleeps in the house or on the premises should be included with the members of the family for which he or she works. A boarder or lodger should be included with the members of the family with which he lodges, but a persons who boards in one place and lodges or rooms at another should be returned as a member of the family at the place where he lodges or rooms. 
Census/survey characteristics
Type Census
Title 1960 Census of Population and Housing
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas).
De jure or de facto De jure
Census/survey day April 1, 1960
Questionnaire The 1960 census used a machine-readable household form. Separate forms were used for each housing unit. Housing questions were included on the same form as the population items. Every fourth enumeration unit received a "long form," containing supplemental sample questions that were asked of all members of the unit. Sample questions are available for all individuals in every unit. Of the units receiving a long form, four-fifths received one version (the 20% questionnaire), and one-fifth received a second version with the same population questions but slightly different housing questions (the 5% questionnaire).
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-100 national random sample drawn by the U.S. Census Bureau
Sample fraction 1%
Sample size (person records) 1,799,888
Sample weights Self-weighting.

Expansion factor = 100.

Units identified in microdata
Dwellings No
Vacant units No
Households Yes
Collective dwellings Yes
Smallest geography State
Unit definitions
Households Dwelling places with fewer than five persons unrelated to a household head, excluding institutions and transient quarters.
Collective dwellings Institutions, transient quarters, and dwelling places with five or more persons unrelated to a household head.
Census/survey characteristics
Type Census
Title 1970 Census of Population and Housing
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas).
De jure or de facto De jure
Census/survey day April 1, 1970
Questionnaire One in five housing units in 1970 received a long form containing supplemental sample questions. There were two versions of the long form, with different inquiries on both housing and population items; 15 percent of households received one version, and 5 percent received the other. Six independent 1 percent public use samples were produced for 1970, three from the 15 percent questionnaire and three from the 5 percent questionnaire. IPUMS-International uses the "Form 2 Metro" sample.
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-100 national random sample drawn by the U.S. Census Bureau
Sample fraction 1%
Sample size (person records) 2,029,666
Sample weights Self-weighting.

Expansion factor = 100.

Units identified in microdata
Dwellings No
Vacant units Yes
Households Yes
Collective dwellings Yes
Smallest geography Metropolitan areas and county groups with 250,000+ residents
Unit definitions
Households Dwelling places with fewer than five persons unrelated to a household head, excluding institutions and transient quarters.
Collective dwellings Institutions, transient quarters, and dwelling places with five or more persons unrelated to a household head.
Census/survey characteristics
Type Census
Title 1980 Census of Population and Housing
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas).
De jure or de facto De jure
Census/survey day April 1, 1980
Questionnaire The 1980 census employed a single long form questionnaire completed by one-half of housing units in places with a population under 2,500 and one-sixth of other housing units.
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-20 national random sample drawn by the U.S. Census Bureau
Sample fraction 5%
Sample size (person records) 11,343,120
Sample weights Self-weighting.

Expansion factor = 100.

Units identified in microdata
Dwellings No
Vacant units Yes
Households Yes
Collective dwellings Yes
Smallest geography PUMAS (Public Use Microdata Areas (PUMAs) containing 100,000 or more residents
Unit definitions
Households Dwelling places with fewer than ten persons unrelated to a household head, excluding institutions and transient quarters.
Collective dwellings Institutions, transient quarters, and dwelling places with ten or more persons unrelated to a household head.
Census/survey characteristics
Type Census
Title 1990 Census of Population and Housing
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas).
De jure or de facto De jure
Census/survey day April 1, 1990
Questionnaire The 1990 census used a single long-form questionnaire completed by one-half of persons in places with a population under 2,500, one-sixth of persons in other tracts and block numbering areas with fewer than 2,000 housing units, and one-eighth of all other areas. Overall, about one-sixth of housing units completed a long form.
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-20 national random sample drawn by the U.S. Census Bureau
Sample fraction 5%
Sample size (person records) 12,501,046
Sample weights Weights computed by census agency should be used for most types of analysis.
Units identified in microdata
Dwellings No
Vacant units Yes
Households Yes
Collective dwellings Yes
Smallest geography PUMAS (Public Use Microdata Areas (PUMAs) containing 100,000 or more residents
Unit definitions
Households Dwelling places with fewer than ten persons unrelated to a household head, excluding institutions and transient quarters.
Collective dwellings Institutions, transient quarters, and dwelling places with ten or more persons unrelated to a household head.
Census/survey characteristics
Type Census
Title 2000 Census of Population and Housing
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas).
De jure or de facto De jure
Census/survey day April 1, 2000
Questionnaire The 2000 census used a long form questionnaire. Long Form Sampling Entities (LFSEs) were used to determine sampling rates. If the smallest LFSE that included all or any part of a block had an estimated housing unit count of less than 800, the housing units in the block were sampled at a 1-in-2 rate. If it had an estimated housing unit count of 800 or more but less than 1,200, units were sampled at a 1-in-4 rate. If a block was not in either of the two previous categories, and was part of an interim census tract with 2,000 or more estimated housing units, units were sampled at a 1-in-8 rate. Housing units in all remaining blocks were sampled at a 1-in-6 rate. When all sampling rates were taken into account across the nation, approximately 1 out of every 6 housing units was included in the Census 2000 sample.
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-20 national random sample drawn by the U.S. Census Bureau
Sample fraction 5%
Sample size (person records) 14,081,466
Sample weights Weights computed by census agency should be used for most types of analysis.
Units identified in microdata
Dwellings No
Vacant units Yes
Households Yes
Collective dwellings Yes
Smallest geography PUMAS (Public Use Microdata Areas (PUMAs) containing 100,000 or more residents
Unit definitions
Households Dwelling places excluding institutions and transient quarters.
Collective dwellings No threshold was applied; in order for a household to be considered group quarters in 2000, it had to be on the list of group quarters that is continuously maintained by the Census Bureau.
Census/survey characteristics
Type Survey
Title 2005 American Community Survey
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas) living in their residence for at least two months, excluding populations living in collective dwellings
De jure or de facto De jure
Census/survey day No specific day
Questionnaire The 2005 American Community Survey employed a single long form questionnaire completed by one of 100 households.
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-100 national random sample drawn by the U.S. Census Bureau
Sample fraction 1%
Sample size (person records) 2,878,380
Sample weights Weights computed by census agency should be used for most types of analysis.
Units identified in microdata
Dwellings No
Vacant units Yes
Households Yes
Collective dwellings No
Smallest geography PUMAS (Public Use Microdata Areas (PUMAs) containing 100,000 or more residents
Unit definitions
Households Dwelling places excluding institutions and transient quarters.
Collective dwellings Not included in microdata sample.
Census/survey characteristics
Type Survey
Title 2010 American Community Survey
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas).
De jure or de facto De jure
Census/survey day No specific day
Questionnaire The 2010 American Community Survey employed a single long form questionnaire completed by one of 100 households and group quarters.
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-100 national random sample drawn by the U.S. Census Bureau
Sample fraction 1%
Sample size (person records) 3,061,692
Sample weights Weights computed by census agency should be used for most types of analysis.
Units identified in microdata
Dwellings No
Vacant units Yes
Households Yes
Collective dwellings Yes
Smallest geography PUMAS (Public Use Microdata Areas (PUMAs) containing 100,000 or more residents
Unit definitions
Households Dwelling places excluding institutions and transient quarters.
Collective dwellings A place where people live or stay, in a group living arrangement, that is owned or managed by an entity or organization providing housing and/or services for the residents. These services may include custodial or medical care as well as other types of assistance, and residency in commonly restricted to those receiving these services. People living in group quarters are usually not related to each other. Group quarters inlcude such places as college residence halls, residential treatment centers, skilled nursing facilities, group homes, military barracks, correctional facilities, and workers' dormitories.
Census/survey characteristics
Type Survey
Title 2015 American Community Survey
Statistical agency U.S. Census Bureau
Population universe Residents of the 50 states (not the outlying areas).
De jure or de facto De jure
Census/survey day No specific day
Questionnaire The 2010 American Community Survey employed a single long form questionnaire completed by one of 100 households and group quarters.
Type of fieldwork Direct and self-enumeration
Estimated undercount No official estimates
Microdata sample characteristics
Sample design 1-in-100 national random sample drawn by the U.S. Census Bureau
Sample fraction 1%
Sample size (person records) 3,147,005
Sample weights Weights computed by census agency should be used for most types of analysis.
Units identified in microdata
Dwellings No
Vacant units Yes
Households Yes
Collective dwellings Yes
Smallest geography PUMAS (Public Use Microdata Areas (PUMAs) containing 100,000 or more residents
Unit definitions
Households Dwelling places excluding institutions and transient quarters.
Collective dwellings A place where people live or stay, in a group living arrangement, that is owned or managed by an entity or organization providing housing and/or services for the residents. These services may include custodial or medical care as well as other types of assistance, and residency in commonly restricted to those receiving these services. People living in group quarters are usually not related to each other. Group quarters inlcude such places as college residence halls, residential treatment centers, skilled nursing facilities, group homes, military barracks, correctional facilities, and workers' dormitories.