Documentation: ACS 2006 -- 2008 (3-Year Estimates)
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Publisher: U.S. Census Bureau
Document: Design and Methodology: American Community Survey
Social Explorer; U.S. Census Bureau; Design and Methodology, American Community Survey. U.S. Government Printing Office, Washington, DC, 2009.
Design and Methodology: American Community Survey
Chapter 6. Survey Rules, Concepts, and Definitions
Interview and residence rules define the universe, or target population, for a survey, and so identify the units and people eligible for inclusion. The 2006−2007 ACS interviewed the resident population living in both housing units (HUs) and group quarters (GQ) facilities. The ACS uses residence rules based on the concept of current residence.

Sections B and C in this chapter detail the interview and residence rules. Section D describes the full set of topics included in the ACS, and is organized into four sections to parallel the organization of the ACS questionnaire: address, HU status, and household information; basic demographic information; detailed housing information; and detailed population information.

Interview Rules
The Census Bureau classifies all living quarters as either HUs or GQ facilities. An HU is a house, an apartment, a group of rooms, or a single room either occupied or intended for occupancy as separate living quarters. GQ facilities are living quarters owned and managed by an entity or organization that provides housing and/or services for the residents. GQ facilities include correctional facilities and such residences as group homes, health care and treatment facilities, and college dormitories.

Interview rules define the scope of data collection by defining the types of places included in the sample frame, as well as the people eligible for inclusion. Beginning in 2006, the ACS included HUs and GQ facilities (only HUs and those living in HUs were included in the 2005 ACS). Like the decennial census, the ACS interviews the resident population without regard to legal status or citizenship, and excludes people residing in HUs only if the residence rules (see below) define their current residence as somewhere other than the sample address.

Residence Rules
Residence rules are the series of rules that define who (if anyone) should be interviewed at a sample address, and who is considered, for purposes of the survey or census, to be a resident. Residence rules decide the occupancy status of each HU and the people whose characteristics are to be collected.

ACS data are collected nearly every day of the year. The surveys residence rules are applied and its reference periods are defined as of the date of the interview. For mail returns, this is when the respondent completes the questionnaire; for telephone and personal visit interviews, it is when the interview is conducted.

Housing Units
The ACS defined the concept of current residence to determine who should be considered residents of sample HUs. This concept is a modified version of a de facto rule in which a time interval is used to determine residency.1 The basic idea behind the ACS current residence concept is that everyone who is currently living or staying at a sample address is considered a current resident of that address, except for those staying there for only a short period of time. For the purposes of the ACS, the Census Bureau defines this short period of time as less than 2 consecutive months (often described as the 2-month rule). Under this rule, anyone who has been or will be living for 2 months or less in the sample unit when the unit is interviewed (either by mail, telephone, or personal visit) is not considered a current resident. This means that their expected length of stay is 2 months or less, not that they have been staying in the sample unit for 2 months or less. In general, people who are away from the sample unit for 2 months or less are considered to be current residents, even though they are not staying there when the interview is conducted, while people who have been or will be away for more than 2 months are considered not to be current residents. The Census Bureau classifies as vacant an HU in which no one is determined to be a current resident.

As noted earlier, residency is determined as of the date of the interview. A person who is living or staying in a sample HU on interview day and whose actual or intended length of stay is more than 2 months is considered a current resident of the unit. That person will be included as a current resident unless he or she, at the time of interview, has been or intends to be away from the unit for a period of more than 2 months. There are three exceptions:
  • Children (below college age) who are away at boarding school or summer camp for more than 2 months are always considered current residents of their parents home.
  • Children who live under joint custody agreements and move between residences are always considered current residents of the sample unit where they are staying at the time of the interview.
  • People who stay at a residence close to work and return regularly to another residence to be with their families are always considered current residents of the family residence.
A person who is staying at a sample HU when the interview is conducted, but has no place where he or she stays for periods of more than 2 months, is considered to be a current resident. A person whose length of stay at the sample HU is for 2 months or less and has another place where he or she stays for periods of more than 2 months is not considered a current resident.

1A de facto rule would include all people who are staying at an address when an interview is conducted, regardless of the time spent at this address. It would exclude individuals away from a regular residence even in they are away only for that one day.

Group Quarters
Residency in GQ facilities is determined by a purely de facto rule. All people staying in the GQ facility when the roster of residents is made and sampled are eligible for selection to be interviewed in the ACS. The GQ sample universe will include all people residing in the selected GQ facility at the time of interview. Data are collected for all people sampled, regardless of their length of stay. Children (below college age) staying at a GQ facility functioning as a summer camp are not considered GQ residents.

Reference Period
As noted earlier, the surveys reference periods are defined relative to the date of the interview. Specifically, the survey questions define the reference periods and always include the date of the interview. When the question does not specify a time frame, respondents are told to refer to the situation on the interview day. When the question mentions a time frame, it refers to an interval that includes the interview day and covers a period before the interview. For example, a question that asks for information about the "past 12 months" would be referring to the previous 12 months relative to the date of the interview.

Structure of the Housing Unit Questionnaire
The ACS questionnaires and survey instruments used to collect data from the HU population are organized into four sections, with each section collecting a specific type of information. The first section verifies basic address information, determines the occupancy status of the HU, and identifies who should be interviewed as part of the ACS household. The second section of the questionnaire collects basic demographic data. The third section collects housing information, and the final section collects population data.

There are data collection instruments for all three data collection modes (mail, telephone, and in-person interviews). A paper questionnaire is used in the mail mode. For telephone, there is a computer-assisted telephone interview (CATI) instrument; for personal interviews, there is a computer-assisted personal interview (CAPI) instrument. This section describes the basic data collection process from a personal visit perspective, but the same basic process is followed in the mail and telephone modes.

Address, Housing Unit Status, and Household Information
During personal visit follow-up, the field representative (FR) first must verify that he or she has reached the sample address, and then determine if the sample address identifies an HU. If an HU is not identified, the address is not eligible and is considered out of scope. Out-of-scope addresses include those determined to be nonexistent because the HU has been demolished, or because they identify a business and not a residential unit. Interviewers use the residence rules to determine whether the sample HU is occupied (at least one person staying in the unit is a current resident) or vacant (no one qualifies as a current resident). Interviewers also apply the residence rules to create a household roster of current occupants to interview. The name of the household respondent and the telephone number are collected in case follow-up contact is needed. The terms below are key for data collection.

Housing Unit (HU)
An HU may be a house, an apartment, a mobile home or trailer, a group of rooms, or a single room that is occupied (or, if vacant, intended for occupancy) as separate living quarters.

Housing Unit Status
All sample addresses are assigned a status as either an occupied, vacant, or temporarily occupied HU, or are assigned a status of delete, indicating that the address does not identify an HU. A temporarily occupied unit is an HU where at least one person is staying, but where no people are current residents; this is considered a type of vacant unit. Deleted units are addresses representing commercial units or HUs that either have been demolished or are nonexistent.

A household is defined as all related or unrelated individuals whose current residence at the time of the ACS interview is the sample address.

Household Roster
This roster is a list of all current residents of the sample address; all of these people will be interviewed.

Household Respondent
One person may provide data for all members of the household. The Census Bureau refers to this person as the household respondent. ACS interviewers try to restrict their household respondents to members who are at least 18 years old but, if necessary, household members who are 15 and older can be interviewed. If no household member can be found to provide the survey information, the interviewer must code the case as a noninterview.

Basic Demographic Information
The basic demographic data of sex, age, relationship, marital status, Hispanic origin, and race are collected at the outset and are considered the most critical data items. They are used in many of the surveys tabulations. Age defines the critical paths and skips patterns used in the instrument/questionnaire. Name also is collected for all household members. One individual in the household must be identified as a reference person to define relationships within the household. The section below provides details of the concept (Person 1) and definitions associated with the basic demographic data.

Reference Person or Householder
One person in each household is designated as the householder. Usually this is the person, or one of the people, in whose name the home is owned, being bought, or rented, and who is listed as "Person 1" on the survey questionnaire. If there is no such person in the household, any adult household member 15 and older can be designated.

Each household members sex is marked as "male" or "female."

Age and Date of Birth
The age classification is based on the age of the person in complete years at the time of interview. Both age and date of birth are used to calculate each person's age on the interview day.

The instrument/questionnaire asks for each household members relationship to the reference person/householder. Categories include both relatives and nonrelatives.

Marital Status
The marital-status question is asked of everyone responding via mail, but only of people 15 and older responding through CATI or CAPI interviews. The response categories are "now married," "widowed," "divorced," "separated," or "never married." Couples who live together (unmarried people, people in common-law marriages) report the marital status they consider the most appropriate.

Hispanic Origin
A person is of Spanish/Hispanic/Latino origin if the persons origin (ancestry) is Mexican, Mexican American, Chicano, Puerto Rican, Cuban, Argentinean, Colombian, Costa Rican, Dominican, Ecuadoran, Guatemalan, Honduran, Nicaraguan, Peruvian, Salvadoran, from other Spanish-speaking countries of the Caribbean or Central or South America, or from Spain. People who identify their origin as Spanish, Hispanic, or Latino may be of any race. Like the concept of race, Hispanic origin is based on self-identification.

According to the Office of Management and Budget (OMB), and as used by the Census Bureau, the concept of race reflects self-identification by people according to the race or races with which they most closely identify. These categories are socio-political constructs and should not be interpreted as scientific or anthropological in nature. The minimum race categories are determined by OMB and required for use in all federal information collections.

Detailed Housing Information
The ACS housing section collects data on physical and financial characteristics of housing. The 2003−2007 ACS questionnaire includes 25 detailed housing questions. For temporarily occupied HUs, selected housing data are collected from the occupants. For vacant units, selected housing data are collected from information given by neighbors, or determined by observation or from another source. This section of the chapter details the concepts associated with some of the housing items.

Units in Structure
All HUs are categorized by the type of structure in which they are located. A structure is a separate building that either has open spaces on all sides, or is separated from other structures by dividing walls that extend from ground to roof. In determining the number of units in a structure, all HUs-both occupied and vacant-are counted. Stores and office space are excluded.

Year Structure Built
This question determines when the building in which the sample address is located was first constructed, not when it was remodeled, added to, or converted. The information is collected for both occupied and vacant HUs. Units that are under construction are not considered housing units until they meet the HU definition-that is, when all exterior windows, doors, and final usable floors are in place. This determines the year of construction. For mobile homes, houseboats, and recreational vehicles, the manufacturers model year is taken as the year the unit was built.

Year Householder Moved Into Unit
This question is collected only for occupied HUs, and refers to the year of the latest move by the householder. If the householder moved back into an HU he or she previously occupied, the year of the last move is reported. If the householder moved from one apartment to another within the same building, the year the householder moved into the present apartment is reported. The intent is to establish the year the current occupancy of the unit by the householder began. The year that the householder moved in is not necessarily the same year other members of the household moved in.

This question determines a range of the acres on which the house or mobile home is located. A major purpose of this item is to identify farm units.

Agricultural Sales
This item refers to the total amount (before taxes and expenses) received from the sale of crops, vegetables, fruits, nuts, livestock and livestock products, and nursery and forest products produced on the property in the 12 months prior to the interview. This item is used to classify HUs as farm or nonfarm residences.

Business on Property
A business must be easily recognizable from the outside. It usually will have a separate outside entrance and the appearance of a business, such as a grocery store, restaurant, or barbershop. It may be attached either to the house or mobile home, or located elsewhere on the property.

The intent of this question is to determine the number of whole rooms in each HU that are used for living purposes. Living rooms, dining rooms, kitchens, bedrooms, finished recreation rooms, enclosed porches suitable for year-round use, and lodgers rooms are included. Excluded are strips or Pullman kitchens, bathrooms, open porches, balconies, halls or foyers, half rooms, utility rooms, unfinished attics or basements, or other unfinished spaces used for storage. A partially divided room is considered a separate room only if there is a partition from floor to ceiling, but not if the partition consists solely of shelves or cabinets.

Bedrooms include only rooms designed to be used as bedrooms; that is, the number of rooms that the respondent would list as bedrooms if the house, apartment, or mobile home were on the market for sale or rent. Included are all rooms intended for use as bedrooms, even if currently they are being used for another purpose. An HU consisting of only one room is classified as having no bedroom.

Plumbing Facilities
Answers to this question are used to estimate the number of HUs that do not have complete plumbing facilities. Complete plumbing facilities include: hot and cold piped water, a flush toilet, and a bathtub or shower. All three facilities must be located inside the house, apartment, or mobile home, but not necessarily in the same room. HUs are classified as lacking complete plumbing facilities when any of the three facilities is not present.

Kitchen Facilities
Answers to this question are used to estimate the number of HUs that do not have complete kitchen facilities. A unit has complete kitchen facilities when it has all three of the following: a sink with piped water, a range or cook top and oven, and a refrigerator. All kitchen facilities must be located in the house, apartment, or mobile home, but not necessarily in the same room. An HU having only a microwave or portable heating equipment, such as a hot plate or camping stove, is not considered to have complete kitchen facilities.

Telephone Service Available
For an occupied unit to be considered as having telephone service available, there must be a telephone in working order and service available in the house, apartment, or mobile home that allows the respondent both to make and receive calls. Households whose service has been discontinued for nonpayment or other reasons are not considered to have telephone service available. Beginning in 2003, the instructions that accompanied the ACS mail questionnaire advised respondents to answer that the house or apartment has telephone service available if cellular telephones are used by household members.

Vehicles Available
These data show the number of passenger cars, vans, and pickup or panel trucks of one-ton capacity or less kept at home and available for the use of household members. Vehicles rented or leased for 1 month or more, company vehicles, and police and government vehicles are included if kept at home and used for nonbusiness purposes. Dismantled or immobile vehicles are excluded, as are vehicles kept at home but used only for business purposes.

House Heating Fuel
House heating fuel information is collected only for occupied HUs. The data show the type of fuel used most to heat the house, apartment, or mobile home.

Selected Monthly Owner Costs
Selected monthly owner costs are the sum of payments for mortgages, deeds of trust, contracts to purchase, or similar debts on the property; real estate taxes; fire, hazard, and flood insurance; utilities (electric, gas, water, and sewer); and fuels (such as oil, coal, kerosene, or wood). These costs also encompass monthly condominium fees or mobile home costs.

Food Stamp Benefit
The Food and Nutrition Service of the U.S. Department of Agriculture (USDA) administers the Food Stamp Program through state and local welfare offices. The Food Stamp Program is the major national income-support program for which all low-income and low-resource households, regardless of household characteristics, are eligible. This question estimates the number of households that received food stamp benefits at any time during the 12-month period before the ACS interview.

All occupied HUs are divided into two categories-owner-occupied and renter occupied. An HU is owner-occupied if the owner or co-owner lives in the unit, even if it is mortgaged or not fully paid for. All occupied HUs that are not owner-occupied, whether they are rented for cash rent or occupied without payment of rent, are classified as renter-occupied.

Contract Rent
Contract rent is the monthly rent agreed to or contracted for, regardless of any furnishings, utilities, fees, meals, or services that may be included.

Gross Rent
Gross rent is the contract rent plus the estimated average monthly cost of utilities and fuels, if these are paid by the renter.

Value of Property
The survey estimates of value of property are based on the respondents estimate of how much the property (house and lot, mobile home and lot, or condominium unit) would sell for. The information is collected for HUs that are owned or being bought, and for vacant HUs that are for sale. If the house or mobile home is owned or being bought, but the land on which it sits is not, the respondent is asked to estimate the combined value of the house or mobile home and the land. For vacant HUs, value is defined as the price asked for the property. This information is obtained from real estate agents, property managers, or neighbors.

Mortgage Status
Mortgage refers to all forms of debt where the property is pledged as security for repayment of the debt.

Mortgage Payment
This item provides the regular monthly amount required to be paid to the lender for the first mortgage on the property.

Detailed Population Information
Detailed population data are collected for all current household members. Some questions are limited to a subset, based on age or other responses. The 2003−2007 ACS included 36 detailed population questions. In Puerto Rico, the place of birth, residence 1 year ago (migration), and citizenship questions differ from those used in the United States. The definitions below refer specifically to the United States. This section describes concepts and definitions for the detailed population items.

Place of Birth
Each person is asked whether he or she was born in or outside of the United States. Those born in the United States are then asked to report the name of the state; people born elsewhere are asked to report the name of the country, or Puerto Rico and U.S. Island Areas.

The responses to this question are used to determine the U.S. citizen and non- U.S. citizen populations and native and foreign-born populations. The foreign-born population includes anyone who was not a U.S. citizen at birth. This includes people who indicate that they are not U.S. citizens, or are citizens by naturalization.

Year of Entry
All respondents born outside of the country are asked for the year in which they came to live in the United States, including people born in Puerto Rico and U.S. Island Areas, those born abroad of an American (U.S. citizen) parent(s), and foreign-born people.

Type of School and School Enrollment
People are classified as enrolled in school if they have attended a regular public or private school or college at any time during the 3 months prior to the time of interview. This question includes instructions to "include only nursery or preschool, kindergarten, elementary school, and schooling which leads to a high school diploma, or a college degree" as a regular school or college. Data are tabulated for people 3 years and older.

Educational Attainment
Educational attainment data are tabulated for people 18 years and older. Respondents are classified according to the highest degree or the highest level of school completed. The question includes instructions for people currently enrolled in school to report the level of the previous grade attended or the highest degree received.

Ancestry refers to a person's ethnic origin or descent, roots or heritage, place of birth, or place of parents ancestors before their arrival in the United States. Some ethnic identities, such as "Egyptian" or "Polish" can be traced to geographic areas outside the United States, while other ethnicities such as "Pennsylvania German" or "Cajun" evolved within the United States.

Language Spoken at Home
Respondents are instructed to mark "Yes" if they sometimes or always speak a language other than English at home, but "No" if the language is spoken only at school or is limited to a few expressions or slang. Respondents are asked the name of the non- English language spoken at home. If the person speaks more than one language other than English at home, the person should report the language spoken most often or, if he or she cannot determine the one spoken most often, the language learned first.

Ability to Speak English
Ability to speak English is based on the persons self-response.

Residence 1 Year Ago (Migration)
Residence 1 year ago is used in conjunction with location of current residence to determine the extent of residential mobility and the resulting redistribution of the population across geographic areas of the country.

Disability is defined as a long-lasting sensory, physical, mental, or emotional condition that makes it difficult for a person to perform activities such as walking, climbing stairs, dressing, bathing, learning, or remembering. It may impede a person from being able to go outside of the home alone or work at a job or business; the definition includes people with severe vision or hearing impairments.

This question asks if the person has given birth in the previous 12 months.

Grandparents as Caregivers
Data are collected on whether a grandchild lives with a grandparent in the household, whether the grandparent has responsibility for the basic needs of the grandchild, and the duration of that responsibility.

Veteran Status
A "civilian veteran" is a person aged 18 years and older who has served (even for a short time), but is not now serving, on active duty in the U.S. Army, Navy, Air Force, Marine Corps, or Coast Guard, or who served in the U.S. Merchant Marine during World War II. People who have served in the National Guard or military reserves are classified as veterans only if they were called or ordered to active duty at some point, not counting the 4 to 6 months of initial training or yearly summer camps. All other civilians aged 18 and older are classified as nonveterans.

Work Status
People aged 16 and older who have worked 1 or more weeks are classified as having "worked in the past 12 months." All other people aged 16 and older are classified as "did not work in the past 12 months."

Place of Work
Data on place of work refer to the location (street address, city/county, state) at which workers carried out their occupational activities during the reference week.

Means of Transportation to Work
Means of transportation to work refers to the principal mode of travel or type of conveyance that the worker usually used to get from home to work during the reference week.

Time Leaving Home to Go to Work
This item covers the time of day that the respondent usually left home to go to work during the reference week.

Travel Time to Work
This question asks the total number of minutes that it usually took the worker to get from home to work during the reference week.

Labor Force Status
These questions on labor force status are designed to identify: (1) people who worked at any time during the reference week; (2) people on temporary layoff who were available for work; (3) people who did not work during the reference week but who had jobs or businesses from which they were temporarily absent (excluding layoffs); (4) people who did not work but were available during the reference week, and who were looking for work during the last 4 weeks; and (5) people not in the labor force.

Industry, Occupation, Class of Worker
Information on industry relates to the kind of business conducted by a person's employing organization; occupation describes the kind of work the person does. For employed people, the data refer to the person's job during the previous week. For those who work two or more jobs, the data refer to the job where the person worked the greatest number of hours. For unemployed people, the data refer to their last job. The information on class of worker refers to the same job as a respondents industry and occupation, and categorizes people according to the type of ownership of the employing organization.

"Total income" is the sum of the amounts reported separately for wage or salary income; net self-employment income; interest, dividends, or net rental or royalty income, or income from estates and trusts; social security or railroad retirement income; Supplemental Security Income; public assistance or welfare payments; retirement, survivor, or disability pensions; and all other income. The estimates are inflation-adjusted using the Consumer Price Index.

Structure of the Group Quarters Questionnaires
The 2006-2007 GQ questionnaire includes all of the population items included on the HU questionnaire, except for relationship. One housing question, food stamp benefit, is asked. Address information is for the GQ facility itself and is collected as part of the automated GQ Facility Questionnaire. The survey information collected from each person selected to be interviewed is entered on a separate questionnaire. The number of questionnaires completed for each GQ facility is the same as the number of people selected, unless a sample person refuses to participate.