This measure divides the age distribution into two equal parts: one-half of the cases falling below the median value and one-half above the value. Median age is computed on the basis of a single year of age distribution.

The most general limitation for many decades has been the tendency of people to overreport ages or years of birth that end in zero or five. This phenomenon is called "age heaping." In addition, the counts in the 1970 and 1980 censuses for people 100 years old and over were substantially overstated. So also were the counts of people aged 69 in 1970 and aged 79 in 1980. Improvements have been made since then in the questionnaire design, and in the allocation procedures which have further minimized these problems. The count of people aged 89 in the 1990 census was not overstated.

Review of detailed 1990 census information indicated that respondents tended to provide their age as of the date they completed the questionnaire, not their age as of April 1, 1990. One reason this happened was that respondents were not specifically instructed to provide their age as of April 1, 1990. Another reason was that data collection efforts continued well past the census date. In addition, there may have been a tendency for respondents to round their age up if they were close to having a birthday. It is likely that approximately 10 percent of people in most age groups were actually one year younger. For most single years of age, the misstatements were largely offsetting. The problem is most pronounced at age zero because people lost to age one probably were not fully offset by the inclusion of babies born after April 1, 1990. Also, there may have been more rounding up to age one to avoid reporting age as zero years. (Age in complete months was not collected for infants under age one.)

The reporting of age one year older than true age on April 1, 1990, is likely to have been greater in areas where the census data were collected later in calendar year 1990. The magnitude of this problem was much less in the 1960, 1970, and 1980 censuses where age was typically derived from respondent data on year of birth and quarter of birth.

These shortcomings were minimized in Census 2000 because age was usually calculated from exact date of birth and because respondents were specifically asked to provide their age as of April 1, 2000. (For more information on the design of the age question, see the section below that discusses "Comparability.")

Age data have been collected in every census. For the first time since 1950, the 1990 data were not available by quarter year of age. This change was made so that coded information could be obtained for both age and year of birth. In 2000, each individual has both an age and an exact date of birth. In each census since 1940, the age of a person was assigned when it was not reported. In censuses before 1940, with the exception of 1880, people of unknown age were shown as a separate category. Since 1960, assignment of unknown age has been performed by a general procedure described as "imputation." The specific procedures for imputing age have been different in each census. (For more information on imputation, see "Accuracy of the Data.")
For more information on age, please telephone 301-457-2428.

Includes people under formally authorized, supervised care or custody in institutions at the time of enumeration. Such people are classified as "patients or inmates" of an institution regardless of the availability of nursing or medical care, the length of stay, or the number of people in the institution. Generally, the institutionalized population is restricted to the institutional buildings and grounds (or must have passes or escorts to leave) and thus have limited interaction with the surrounding community. Also, they are generally under the care of trained staff who have responsibility for their safekeeping and supervision.

The type of institution was determined as part of census enumeration activities. For institutions that specialize in only one specific type of service, all patients or inmates were given the same classification. For institutions that had multiple types of major services (usually general hospitals and Veterans Administration hospitals), patients were classified according to selected types of wards. For example, in psychiatric wards of hospitals, patients were classified in "mental (psychiatric) hospitals"; in general hospital wards for people with chronic diseases, patients were classified in "other hospitals for the chronically ill." Each patient or inmate was classified in only one type of institution. Institutions include the following types:

Comprises a heterogeneous group of places providing continuous nursing and other services to patients. The majority of patients are elderly, although people who require nursing care because of chronic physical conditions may be found in these homes regardless of their age. Included in this category are skilled-nursing facilities, intermediate-care facilities, long-term care rooms in wards or buildings on the grounds of hospitals, or long-term care rooms/nursing wings in congregate housing facilities. Also included are nursing, convalescent, and rest homes, such as soldiers, sailors, veterans, and fraternal or religious homes for the aged, with nursing care.

Includes hospitals or wards for the criminally insane not operated by a prison and psychiatric wards of general hospitals and veterans hospitals. Patients receive supervised medical/nursing care from formally trained staff.

Includes hospitals for patients who require long-term care, including those in military hospitals and wards for the chronically ill located on military bases; or other hospitals or wards for the chronically ill, which include tuberculosis hospitals or wards; wards in general and Veterans Administration hospitals for the chronically ill; neurological wards; hospices and homes for chronically ill patients; wards for patients with Hansens Disease (leprosy) and other incurable diseases; and other unspecified wards for the chronically ill. Patients who had no usual home elsewhere were enumerated as part of the institutional population in the wards of general and military hospitals. Most hospital patients are at the hospital temporarily and were enumerated at their usual place of residence. In some census products, patients in hospitals or wards for the chronically ill are classified in three categories: (1) military hospitals or wards for chronically ill, (2) other hospitals or wards for chronically ill, and (3) hospices or homes for chronically ill.

Includes those institutions such as wards in hospitals for the mentally retarded and intermediate-care facilities for the mentally retarded that provide supervised medical/nursing care from formally trained staff.

Includes three types of institutions: institutions for the blind, those for the deaf, and orthopedic wards and institutions for the physically handicapped. Institutions for people with speech problems are classified with "institutions for the deaf." The category "orthopedic wards and institutions for the physically handicapped" includes those institutions providing relatively long-term care to accident victims and to people with polio, cerebral palsy, and muscular dystrophy.

Includes hospitals and wards for drug/alcohol abuse. These facilities are equipped medically and designed for the diagnosis and treatment of medical or psychiatric illnesses associated with alcohol or drug abuse. Patients receive supervised medical care from formally trained staff.

Includes maternity, neonatal, pediatric (including wards for boarder babies), and surgical wards of hospitals and wards for people with infectious diseases. If not shown separately, this category includes wards in military hospitals for patients who have no usual home elsewhere.

(See above definition for "Wards in general hospitals for patients who have no usual home elsewhere.")

Includes homes, schools, and other institutions providing care for children (short- or long-term care). Juvenile institutions include the following types:

Includes people who live in group quarters other than institutions. Includes staff residing in military and nonmilitary group quarters on institutional grounds who provide formally authorized, supervised care or custody for the institutionalized population.

For Census 2000, the definition of the institutionalized population was consistent with the definition used in the 1990 census. As in 1990, the definition of "care" only includes people under organized medical or formally authorized, supervised care or custody.

In Census 2000, the 1990 and 1980 rule of classifying ten or more unrelated people living together as living in noninstitutional group quarters was dropped. In 1970, the criteria was six or more unrelated people.

Several changes have occurred in the tabulation of specific types of group quarters. In Census 2000, police lockups were included with local jails and other confinement facilities, and homes for unwed mothers were included in "Other group homes;" in 1990, these categories were shown separately. For the first time, Census 2000 tabulates separately the following types of group quarters: military hospitals or wards for the chronically ill, other hospitals or wards for the chronically ill, hospices or homes for the chronically ill, wards in military hospitals with patients who have no usual home elsewhere, wards in general hospitals with patients who have no usual home elsewhere, and job corps and vocational training facilities. For Census 2000, rooming and boarding houses were classified as housing units rather than group quarters as in 1990.

As in 1990, workers dormitories were classified as group quarters regardless of the number of people sharing the dormitory. In 1980, ten or more unrelated people had to share the dorm for it to be classified as a group quarters. In 1960, data on people in military barracks were shown only for men. In subsequent censuses, they include both men and women.

The phrase "institutionalized persons" in 1990 data products was changed to "institutionalized population" for Census 2000. In 1990, the Census Bureau used the phrase "other persons in group quarters" for people living in noninstitutional group quarters. In 2000, this group is referred to as the "noninstitutionalized population." The phrase "staff residents" was used for staff living in institutions in both 1990 and 2000.

In Census 2000, the category "emergency and transitional shelters" includes emergency shelters, transitional shelters, and shelters for children who are runaways, neglected, or without conventional housing. Those people tabulated at shelters for abused women, soup kitchens, regularly scheduled mobile food vans, and targeted nonsheltered outdoor locations were included in the category "other noninstitutional group quarters." Each of these categories were enumerated from March 27-29, 2000, during Service-Based enumeration. (For more information on the "Service- Based Enumeration" operation, see "Collection and Processing Procedures.")
For more information on group quarters, please telephone 301-457-2378.

There are two important changes to the Hispanic origin question for Census 2000. First, the sequence of the race and Hispanic origin questions for Census 2000 differs from that in 1990; in 1990, the race question preceded the Hispanic origin question. Testing prior to Census 2000 indicated that response to the Hispanic origin question could be improved by placing it before the race question without affecting the response to the race question. Second, there is an instruction preceding the Hispanic origin question indicating that respondents should answer both the Hispanic origin and the race questions. This instruction was added to give emphasis to the distinct concepts of the Hispanic origin and race questions, and to emphasize the need for both pieces of information.

Furthermore, there has been a change in the processing of the Hispanic origin and race responses. In the 1990 census, respondents provided Hispanic origin responses in the race question and race responses in the Hispanic origin question. In 1990, the Hispanic origin question and the race question had separate edits; therefore, although information may have been present on the questionnaire, it was not fully utilized due to the discrete nature of the edits. However, for Census 2000 there is a joint race and Hispanic origin edit, which can utilize Hispanic origin and race information that was reported in the inappropriate question.
For more information on Hispanic or Latino, please telephone 301-457-2403.

A household includes all of the people who occupy a housing unit. A housing unit is a house, an apartment, a mobile home, a group of rooms, or a single room occupied (or if vacant, intended for occupancy) as separate living quarters. Separate living quarters are those in which the occupants live separately from any other people in the building and that have direct access from the outside of the building or through a common hall. The occupants may be a single family, one person living alone, two or more families living together, or any other group of related or unrelated people who share living quarters.

In 100-percent tabulations, the count of households or householders always equals the count of occupied housing units. In sample tabulations, the numbers may differ as a result of the weighting process.

The phrase "Coverage Improvement Adjustment" was included in the table outlines and the technical documentation before the review, analysis, and recommendation on whether to adjust Census 2000 data for coverage improvement was completed. As the data are not adjusted, a zero (0) will appear. This phrase does not refer to any other outreach or collection opertions that were introduced to improve coverage in Census 2000.

An unrelated individual is: (1) a householder living alone or with nonrelatives only, (2) a household member who is not related to the householder, or (3) a person living in group quarters who is not an inmate of an institution.

A family includes a householder and one or more other people living in the same household who are related to the householder by birth, marriage, or adoption. All people in a household who are related to the householder are regarded as members of his or her family. A household can contain only one family for purposes of census tabulations. Not all households contain families since a household may be a group of unrelated people or one person living alone.

Families are classified by type as either a "married-couple family" or an "other family" according to the presence of a spouse. "Other family" is further broken out according to the sex of the householder. The data on family type are based on answers to questions on sex and relationship that were asked on a 100-percent basis.

A measure obtained by dividing the number of people in families by the total number of families (or family householders). In cases where this measure is tabulated by race or Hispanic origin, the race or Hispanic origin refers to that of the householder rather than to the race or Hispanic origin of each individual.

An unmarried-partner household is a household other than a "married-couple household" that includes a householder and an "unmarried partner." An "unmarried partner" can be of the same sex or of the opposite sex of the householder. An "unmarried partner" in an "unmarried-partner household" is an adult who is unrelated to the householder, but shares living quarters and has a close personal relationship with the householder.

A person having origins in any of the original peoples of Europe, the Middle East, or North Africa. It includes people who indicate their race as White or report entries such as Irish, German, Italian, Lebanese, Near Easterner, Arab, or Polish.

A person having origins in any of the Black racial groups of Africa. It includes people who indicate their race as Black, African Am., or Negro, or provide written entries such as African American, Afro American, Kenyan, Nigerian, or Haitian.

A person having origins in any of the original peoples of North and South America (including Central America) and who maintain tribal affiliation or community attachment. It includes people who classified themselves as described below.

A person having origins in any of the original peoples of the Far East, Southeast Asia, or the Indian subcontinent including, for example, Cambodia, China, India, Japan, Korea, Malaysia, Pakistan, the Philippine Islands, Thailand, and Vietnam. It includes "Asian Indian," "Chinese," "Filipino," "Korean," "Japanese," "Vietnamese," and "Other Asian."

A person having origins in any of the original peoples of Hawaii, Guam, Samoa, or other Pacific Islands. It includes people who indicate their race as "Native Hawaiian," "Guamanian or Chamorro," "Samoan," and "Other Pacific Islander."

Includes all other responses not included in the "White," "Black or African American," "American Indian or Alaska Native," "Asian," and "Native Hawaiian or Other Pacific Islander" race categories described above. Respondents providing write-in entries such as multiracial, mixed, interracial, or a Hispanic/Latino group (for example, Mexican, Puerto Rican, or Cuban) in the "Some other race" write-in space are included in this category.

People may have chosen to provide two or more races either by checking two or more race response check boxes, by providing multiple write-in responses, or by some combination of check boxes and write-in responses. The race response categories shown on the questionnaire are collapsed into the five minimum race groups identified by the OMB, and the Census Bureau "Some other race" category. For data product purposes, "Two or more races" refers to combinations of two or more of the following race categories:

1. White
2. Black or African American
3. American Indian and Alaska Native
4. Asian
5. Native Hawaiian and Other Pacific Islander
6. Some other race

There are 57 possible combinations (see Figure B-1) involving the race categories shown above. Thus, according to this approach, a response of "White" and "Asian" was tallied as two or more races, while a response of "Japanese" and "Chinese" was not because "Japanese" and "Chinese" are both Asian responses. Tabulations of responses involving reporting of two or more races within the American Indian and Alaska Native, Asian, or Native Hawaiian and Other Pacific Islander categories are available in other data products.

Given the many possible ways of displaying data on two or more races, data products will provide varying levels of detail. The most common presentation shows a single line indicating "Two or more races." Some data products provide totals of all 57 possible combinations of two or more races, as well as subtotals of people reporting a specific number of races, such as people reporting two races, people reporting three races, and so on.

In other presentations on race, data are shown for the total number of people who reported one of the six categories alone or in combination with one or more other race categories. For example, the category "Asian alone or in combination with one or more other races" includes people who reported Asian alone and people who reported Asian in combination with White, Black or African American, Native Hawaiian and Other Pacific Islander, and Some other race. This number, therefore, represents the maximum number of people who reported as Asian in the question on race. When this data presentation is used, the individual race categories will add to more than the total population because people may be included in more than one category.

During 100-percent processing of Census 2000 questionnaires, subject-matter specialists reviewed and coded written entries from four response categories on the race item American Indian or Alaska Native, Other Asian, Other Pacific Islander, and Some other race. The Other Asian and Other Pacific Islander response categories shared the same write-in area on the questionnaire.

The data on race in Census 2000 are not directly comparable to those collected in previous censuses. The October 1997 revised standards issued by the OMB led to changes in the question on race for Census 2000. The Census 2000 Dress Rehearsal data were the first to reflect these changes. First, respondents were allowed to select more than one category for race. Second, the sequence of the questions on race and Hispanic origin changed. In 1990, the question on race (Item 4) preceded the question on Hispanic origin (Item 7) with two intervening questions. For Census 2000, the question on race immediately follows the question on Hispanic origin. Third, there were terminology changes to the response categories, such as spelling out "American" instead of "Amer." for the American Indian or Alaska Native category; and adding "Native" to the Hawaiian response category. The 1990 category "Other race" was renamed "Some other race."

Other differences that may affect comparability involve the individual categories on the Census 2000 questionnaire. The 1990 category, "Asian and Pacific Islander" was separated into two categories, "Asian" and "Native Hawaiian and Other Pacific Islander." Accordingly, on the Census 2000 questionnaire, there were seven Asian categories and four Native Hawaiian and Other Pacific Islander categories. The two residual categories, "Other Asian" and "Other Pacific Islander," replaced the 1990 single category "Other API." The 1990 categories "American Indian," "Eskimo," and "Aleut" were combined into "American Indian and Alaska Native." American Indians and Alaska Natives can report one or more tribes.

As in 1990, people who reported a Hispanic or Latino ethnicity in the question on race and did not mark a specific race category were classified in the "Some other race" category ("Other race" in 1990). They commonly provided a write-in entry such as Mexican, Puerto Rican, or Latino. In the 1970 census, most of these responses were included in the "White" category. In addition, some ethnic entries that in 1990 may have been coded as White or Black are now shown in the "Some other race group."

For Puerto Rico, separate questions on race and Hispanic origin were included on their Census 2000 questionnaire, identical to the questions used in the United States. The 1950 census was the last census to include these questions on the Puerto Rico questionnaire.

Census 2000 included an automated review, computer edit, and coding operation on a 100- percent basis for the write-in responses to the race question, similar to that used in the 1990 census. Write-in responses such as Laotian or Thai, and Guamanian or Tongan were reviewed, coded, and tabulated as "Other Asian" and "Other Pacific Islander," respectively, in the census. All tribal entries were coded as either American Indian or as Alaska Native.
For more information on race, please telephone 301-457-2402.

Figure B-1. Two or More Races (57 Possible Specified Combinations)

1. White; Black or African American


2. White; American Indian and Alaska Native


3. White; Asian


4. White; Native Hawaiian and Other Pacific Islander


5. White; Some other race


6. Black; American Indian and Alaska Native


7. Black; Asian


8. Black; Native Hawaiian and Other Pacific Islander


9. Black; Some other race


10. American Indian and Alaska Native; Asian


11. American Indian and Alaska Native; Native Hawaiian or Other Pacific Islander


12. American Indian and Alaska Native; Some other race


13. Asian; Native Hawaiian and Other Pacific Islander


14. Asian; Some other race


15. Native Hawaiian and Other Pacific Islander; Some other race


16. White; Black; American Indian and Alaska Native


17. White; Black; Asian


18. White; Black; Native Hawaiian and Other Pacific Islander


19. White; Black; Some other race


20. White; American Indian and Alaska Native; Asian


21. White; American Indian and Alaska Native; Native Hawaiian and Other Pacific Islander


22. White; American Indian and Alaska Native; Some other race


23. White; Asian; Native Hawaiian and Other Pacific Islander


24. White; Asian; Some other race


25. White; Native Hawaiian and Other Pacific Islander; Some other race


26. Black; American Indian and Alaska Native; Asian


27. Black; American Indian and Alaska Native; Native Hawaiian and Other Pacific Islander


28. Black; American Indian and Alaska Native; Some other race


29. Black; Asian; Native Hawaiian and Other Pacific Islander


30. Black; Asian; Some other race


31. Black; Native Hawaiian and Other Pacific Islander; Some other race


32. American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific Islander


33. American Indian and Alaska Native; Asian; Some other race


34. American Indian and Alaska Native; Native Hawaiian and Other Pacific Islander; Some other race


35. Asian; Native Hawaiian and Other Pacific Islander; Some other race


36. White; Black; American Indian and Alaska Native; Asian


37. White; Black; American Indian and Alaska Native; Native Hawaiian and Other Pacific Islander


38. White; Black; American Indian and Alaska Native; Some other race


39. White; Black; Asian; Native Hawaiian and Other Pacific Islander


40. White; Black; Asian; Some other race


41. White; Black; Native Hawaiian and Other Pacific Islander; Some other race


42. White; American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific mIslander


43. White; American Indian and Alaska Native; Asian; Some other race


44. White; American Indian and Alaska Native; Native Hawaiian and Other Pacific Islander; Some other race


45. White; Asian; Native Hawaiian and Other Pacific Islander; Some other race


46. Black; American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific Islander


47. Black; American Indian and Alaska Native; Asian; Some other race


48. Black; American Indian and Alaska Native; Native Hawaiian and Other Pacific Islander; Some other race


49. Black; Asian; Native Hawaiian and Other Pacific Islander; Some other race


50. American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific Islander; Some other race


51. White; Black; American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific Islander


52. White; Black; American Indian and Alaska Native; Asian; Some other race


53. White; Black; American Indian and Alaska Native; Native Hawaiian and Other Pacific Islander; Some other race


54. White; Black; Asian; Native Hawaiian and Other Pacific Islander; Some other race


55. White; American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific mIslander; Some other race


56. Black; American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific Islander; Some other race


57. White; Black; American Indian and Alaska Native; Asian; Native Hawaiian and Other Pacific Islander; Some other race

A measure derived by dividing the total number of males by the total number of females and multiplying by 100.

A question on the sex of individuals has been asked of the total population in every census.
For more information on sex, please telephone 301-457-2378.

A housing unit may be a house, an apartment, a mobile home, a group of rooms, or a single room that is occupied (or, if vacant, is intended for occupancy) as separate living quarters. Separate living quarters are those in which the occupants live separately from any other individuals in the building and that have direct access from outside the building or through a common hall. For vacant units, the criteria of separateness and direct access are applied to the intended occupants whenever possible. If that information cannot be obtained, the criteria are applied to the previous occupants.

Both occupied and vacant housing units are included in the housing unit inventory. Boats, recreational vehicles (RVs), vans, tents, and the like are housing units only if they are occupied as someones usual place of residence. Vacant mobile homes are included provided they are intended for occupancy on the site where they stand. Vacant mobile homes on dealers lots, at the factory, or in storage yards are excluded from the housing inventory. Also excluded from the housing inventory are quarters being used entirely for nonresidential purposes, such as a store or an office, or quarters used for the storage of business supplies or inventory, machinery, or agricultural products.

A housing unit is occupied if it is the usual place of residence of the person or group of people living in it at the time of enumeration or if the occupants are only temporarily absent; that is, away on vacation or business. The occupants may be a single family, one person living alone, two or more families living together, or any other group of related or unrelated people who share living quarters.

Occupied rooms or suites of rooms in hotels, motels, and similar places are classified as housing units only when occupied by permanent residents; that is, people who consider the hotel as their usual place of residence or who have no usual place of residence elsewhere.

If any of the occupants in rooming or boarding houses, congregate housing, or continuing care facilities live separately from others in the building and have direct access, their quarters are classified as separate housing units.

The living quarters occupied by staff personnel within any group quarters are separate housing units if they satisfy the housing unit criteria of separateness and direct access; otherwise, they are considered group quarters.

A housing unit is vacant if no one is living in it at the time of enumeration, unless its occupants are only temporarily absent. Units temporarily occupied at the time of enumeration entirely by people who have a usual residence elsewhere are classified as vacant.

New units not yet occupied are classified as vacant housing units if construction has reached a point where all exterior windows and doors are installed and final usable floors are in place.

Vacant units are excluded from the housing inventory if they are open to the elements; that is, the roof, walls, windows, and/or doors no longer protect the interior from the elements. Also excluded are vacant units with a sign that they are condemned or they are to be demolished.

The first Census of Housing in 1940 established the "dwelling unit" concept. Although the term became "housing unit" and the definition was modified slightly in succeeding censuses, the housing unit definition remained essentially comparable between 1940 and 1990. Since 1990, two changes were made to the housing unit definition.

The first change eliminated the concept of "eating separately." The elimination of the eating criterion is more in keeping with the United Nations definition of a housing unit that stresses the entire concept of separateness rather than the specific "eating" element. Although we previously included the "eating separately" criterion in the definition of a housing unit, data were not collected that allowed us to distinguish whether the occupants ate separately from any other people in the building. (Questions that asked households about their eating arrangements have not been included in the census after 1970.) Therefore, the current definition better reflects the information that is used in the determination of a housing unit.

The second change for Census 2000 eliminated the "number of nonrelatives" criterion; that is, "9 or more people unrelated to the householder" which caused a conversion of housing units to group quarters. This change was prompted by the following considerations: (1) there were relatively few such conversions made as a result of this rule in 1990; (2) household relationship and housing data were lost by converting these units to group quarters; and (3) there was no empirical support for establishing a particular number of nonrelatives as a threshold for these conversions.

In 1960, 1970, and 1980, vacant rooms in hotels, motels, and other similar places where 75 percent or more of the accommodations were occupied by permanent residents were counted as part of the housing inventory. We intended to classify these vacant units as housing units in the 1990 census. However, an evaluation of the data collection procedures prior to the 1990 census indicated that the concept of permanency was a difficult and confusing procedure for enumerators to apply correctly. Consequently, in the 1990 census, vacant rooms in hotels, motels, and similar places were not counted as housing units. In Census 2000, we continued the procedure adopted in 1990.
For more information on housing units, please telephone 301-457-3191.

A housing unit is owner occupied if the owner or co-owner lives in the unit even if it is mortgaged or not fully paid for. The owner or co-owner must live in the unit and usually is Person 1 on the questionnaire. The unit is "Owned by you or someone in this household with a mortgage or loan" if it is being purchased with a mortgage or some other debt arrangement, such as a deed of trust, trust deed, contract to purchase, land contract, or purchase agreement. The unit is also considered owned with a mortgage if it is built on leased land and there is a mortgage on the unit.

A housing unit is "Owned by you or someone in this household free and clear (without a mortgage or loan)" if there is no mortgage or other similar debt on the house, apartment, or mobile home including units built on leased land if the unit is owned outright without a mortgage. Although owner-occupied units are divided between mortgaged and owned free and clear on the questionnaire, census data products containing 100-percent data show only total owner-occupied counts. More extensive mortgage information is collected on the long-form questionnaire.

All occupied housing units that are not owner occupied, whether they are rented for cash rent or occupied without payment of cash rent, are classified as renter occupied. "No cash rent" units are separately identified in the rent tabulations. Such units are generally provided free by friends or relatives or in exchange for services, such as resident manager, caretaker, minister, or tenant farmer. Housing units on military bases also are classified in the "No cash rent" category. "Rented for cash rent" includes units in continuing care, sometimes called life care arrangements. These arrangements usually involve a contract between one or more individuals and a service provider guaranteeing the individual shelter, usually a house or apartment, and services, such as meals or transportation to shopping or recreation.

Data on tenure have been collected since 1890. In 1990, the response categories were expanded to allow the respondent to report whether the unit was owned with a mortgage or loan, or free and clear (without a mortgage). The distinction between units owned with a mortgage and units owned free and clear was added in 1990 to improve the count of owner-occupied units. Research after the 1980 census indicated some respondents did not consider their units owned if they had a mortgage. In Census 2000, we continued with the same tenure categories used in the 1990 census.
For more information on tenure, please telephone 301-457-3191.

These are vacant units offered "for rent" and vacant units offered either "for rent or for sale."

These are vacant units offered "for sale only," including units in cooperatives and condominium projects if the individual units are offered "for sale only."

If any money rent has been paid or agreed upon but the new renter has not moved in as of the date of enumeration, or if the unit has recently been sold but the new owner has not yet moved in, the vacant unit is classified as "rented or sold, not occupied."

These are vacant units used or intended for use only in certain seasons, for weekends, or other occasional use throughout the year. Seasonal units include those used for summer or winter sports or recreation, such as beach cottages and hunting cabins. Seasonal units also may include quarters for such workers as herders and loggers. Interval ownership units, sometimes called shared-ownership or time-sharing condominiums, also are included in this category.

These include vacant units intended for occupancy by migratory workers employed in farm work during the crop season. (Work in a cannery, a freezer plant, or a foodprocessing plant is not farm work.)

If a vacant unit does not fall into any of the classifications specified above, it is classified as "other vacant." For example, this category includes units held for occupancy by a caretaker or janitor, and units held for personal reasons of the owner.

Available housing units are vacant units that are for sale only or for rent.

The proportion of the housing inventory that is available for sale only or for rent. It is computed by dividing the number of available units by the sum of the occupied units and the number of available units, and then multiplying by 100.

The proportion of the homeowner housing inventory that is vacant for sale. It is computed by dividing the number of vacant units for sale only by the sum of the owner-occupied units and vacant units that are for sale only, and then multiplying by 100.

The proportion of the rental inventory that is vacant for rent. It is computed by dividing the number of vacant units for rent by the sum of the renter-occupied units and the number of vacant units for rent, and then multiplying by 100.

Data on vacancy status have been collected since 1940. Since 1990, we have used the category "For seasonal, recreational, or occasional use." In earlier censuses, separate categories were used to collect data on these types of vacant units. Also, in 1970 and 1980, housing characteristics generally were presented only for year-round units. Beginning in 1990 and continuing into Census 2000, housing characteristics are shown for all housing units.
For more information on vacancy status, please telephone 301-457-3191.