DEFINITIONS AND EXPLANATIONS

Except for the few instances noted below, the concepts and definitions used in the 1955 quarterly survey are identical with those used in the 1950 Census. However, the content of the 1955 survey differed slightly from the 1950 Census. In 1955, but not in 1950, information was collected on the number of bedrooms, duration of vacancy, and inclusion of utilities in rent. On the other hand, the 1950 Census included questions on plumbing facilities and year built. In both years, information was obtained on number of rooms in the unit, number of dwelling units in the structure, condition, status, monthly rent, and sale price.

Urban-rural residence.--Urban housing comprises all dwelling units in (a) places of 2,500 inhabitants or more incorporated as cities, boroughs, and villages, (b) incorporated towns of 2,500 inhabitants or more except in New England, New York, and Wisconsin, where "towns" are simply minor civil divisions of counties, (c) the densely settled urban fringe around cities of 50,000 inhabitants or more, including both incorporated and unincorporated areas, and (d) unincorporated places of 2,500 inhabitants or more outside any urban fringe. The remaining dwelling units are classified as rural.

The urban classification thus includes, in addition to dwelling units in urban places, the housing in closely settled areas in the vicinity of large cities. These areas, known as the "urban fringe," were established to conform as nearly as possible to the actual boundaries of thickly settled territory, usually characterized by a closely spaced street pattern. Urban fringe areas were set up for each city of 50,000 inhabitants or more just prior to the 1950 Census. Thus, some concentrations of new housing just outside the urban fringe may be classified as rural.

The definition for urban housing, given above, is that used for the 1950 Census. The identification and boundaries of urban places and urban fringes established for the 1950 Census were not brought up to date for the 1955 statistics so that the designation of urban housing is the same for both years.

The rural classification comprises a variety of residences, such as isolated homes in the open country and dwelling units in villages and hamlets of fewer than 2,500 inhabitants.

Nonfarm residence.--Nonfarm dwelling units are defined to include all units not on farms. For occupied units, the farm-nonfarm classification 1s based on the respondent's reply to the question, "Is this house on a farm?" Farm residence is, therefore,

Standard metropolitan areas.--Except in New England, a standard metropolitan area is a county or group of contiguous counties which contains at least one city of 50,000 inhabitants or more at the time of the 1950 Census. Counties contiguous to the one containing such a city are included in a standard metropolitan area if according to certain criteria they are essentially metropolitan in character and socially and economically integrated with the central city. In New England, towns and cities were the units used in defining standard metropolitan areas. Here a population density criterion was applied rather than the criteria relating to metropolitan character.

Statistics for "inside standard metropolitan areas" in table 2 are for all vacant dwelling units-urban and rural, farm and nonfarm--which are located within the counties and places comprising standard metropolitan areas.

For a list of all standard metropolitan areas, and their constituent counties (cities, towns), refer to the individual chapters (or bulletins) in the 1950 Census of Housing, Volume I, General Characteristics; or to the 1950 Census of Population, Volume I, Number of Inhabitants, or Volume II, Characteristics of the Population, Part 1, United States Summary.

The standard metropolitan areas were established at the time of the 1950 Census. Both the 1950 and 1955 statistics relate to these same (168) areas. A map identifying the standard metropolitan areas and their location is given on page 12 of this report.

Dwelling units --In general, a dwelling unit is a group of rooms or a single room. occupied or intended for occupancy as separate living quarters by a family or other group of persons living together or by a person living alone.

Ordinarily, a dwelling unit is a house, an apartment, or a flat. A dwelling unit may be located

A group of rooms, occupied or intended for occupancy as separate living quarters, is a dwelling unit if it has separate cooking equipment or separate entrance. A single room, occupied or intended

for occupancy as separate living quarters, is a dwelling unit if it has separate cooking equipment or if it constitutes the only living quarters in the structure. Each apartment in a regular apartment house is a dwelling unit even though it may not have separate cooking equipment. Apartments in residential hotels are dwelling units if they have separate cooking equipment or consist of two or more rooms. Since it is customary in some localities for the intended occupants to furnish their own cooking equipment, vacant units were considered as having cooking equipment if they were currently equipped with or if the last occupants had such equipment.

Nonresident dwelling units.--A nonresident dwelling unit is a unit which is occupied temporar1ly by persons who usually live elsewhere, provided the usual place of residence is held for the household and is not offered for rent or for sale. For example, a beach cottage occupied at the time of enumeration by a family which has a usual place of residence in the city is considered a nonresident unit. Their house in the city would be reported "occupied" and would be included in the count occupied units since the occupants are only temporarily absent.

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vacant units as dilapidated, or not dilapidated but held off the market, as the case may be. In the 1950 reports, the nonresident units were shown as a separate category; for comparison with the 1955 results, however, these units were distributed among seasonal, dilapidated, and not dilapidated units held

off the market.

Vacant dwelling units.--A dwelling unit (furnished or unfurnished) is vacant if no persons were living in it at the time of enumeration, except when its occupants were only temporarily absent. Dilapidated vacant dwelling units were included if they were intended for occupancy as living quarters; however, if the unit was unfit for use and beyond repair so that it was no longer considered living quarters, it was excluded from the inventory. New units not yet occupied were enumerated as vacant dwelling units if construction had proceeded to the point that all the exterior windows and doors were installed and final usable floors were in place; otherwise, potential units under construction were not included. Unoccupied units held off the market for various reasons and units recently rented or sold but not yet occupied are considered vacant.

Year-round vacant units.--Year-round units are those intended for year-round occupancy, even though they may not be in use the year round. In resort areas, a dwelling unit which is usually occupied on a year-round basis was considered a year-round unit. On the other hand, a dwelling unit located in the closely built-up area of a nonresort city was considered a "year-round" unit even though it may be occupied only part of the year. As indicated above, year-round units temporarily occupied by persons with usual residence elsewhere are included with year-round vacant units.

Condition of dwelling unit.--The structural condition of a dwelling unit is considered one of the measures of the quality of housing. To measure condition, the vacant dwelling units were classified as "not dilapidated" or "dilapidated."

The enumerator determined the condition of the dwelling unit on the basis of his own observation. He was instructed to appraise the condition of units uniformly, regardless of the neighborhood. The enumerator was provided with detailed written instructions and with pictures illustrating the concepts "deterioration" and "inadequate original construction."

Although the enumerator was provided with detailed oral and written instructions and with visual aids, it was not possible to eliminate completely the element of judgment in the enumeration of this item. It is possible that some enumerators obtained too large or too small a count of dilapidated units. However, with the large number of enumerators involved, it is likely that such deviations tend to be offsetting.

Available vacant units.--This category provides a measure of vacant dwelling units which are on the housing market for year-round occupancy. It consists of units which are for year-round occupancy, are not dilapidated, and are being offered for rent or sale. Excluded are seasonal units, dilapidated units, and units already rented or sold or not on the rental or sale market for other reasons. The count of available vacancies constitutes a more effective measure of the supply of vacant housing than does the count of total vacancies. This category is comparable with the 1950 category "Nonseasonal not dilapidated, for rent or sale."

The category "For rent" consists of vacant units offered for rent as well as those being offered both for rent and for sale. The category "For sale only" is limited to units for sale and not for rent. If a unit was located in a multi-unit structure which was for sale as an entire structure, and if the unit was not for rent, it was reported as "held off market." However, in a 2- or 3-dwelling-unit structure which was for sale, the unit intended to be occupied by the owner was reported as for sale.

Vacant units rented or sold.--This group consists of year-round not dilapidated vacant units which have been rented or sold but the new renters or owners have not moved in as of the day of enumeration. In the 1950 statistics, such units are shown in combination with year-round not dilapidated vacant units held off the market.

Vacant units held off the market.--Included in this category are year-round not dilapidated units which were vacant for reasons other than those men

tioned above: for example, held for occupancy of a caretaker, Janitor, and the like; held for settlement of estate; held for personal reasons of the owner; temporarily used for storage; and temporarily occupied by persons who have a usual place of residence elsewhere. In the 1950 statistics, such units are shown in combination with year-round not dilapidated vacant units, rented or sold, as "nonseasonal not dilapidated, not for rent or sale" units.

Number of rooms.--All rooms

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which are to be used, or are suitable for use, as living quarters were counted in determining the number of rooms in the dwelling unit. Included are kitchens, bedrooms, dining rooms, living rooms, and permanently enclosed sunporches of substantial size; and finished basement or attic rooms, recreation rooms, or other suitable for use as living quarters. A kitchenette or half-room which is partitioned off from floor to ceiling was counted as a separate room, but a combined kitchenette and dinette separated only by shelves or cabinets was counted as only one room. Not counted as rooms were bathrooms, strip or pullman kitchens, halls or foyers, alcoves, pantries, laundries, closets or storage space, and unfinished basement or attic rooms not suitable for living quarters.

The median number of rooms is the theoretical value which divides the dwelling units equally, onehalf having more rooms and one-half having fewer rooms than the median. In the computation of the median, a continuous distribution was assumed. For example, when the median was in the 3-room group, the lower and upper limits were assumed to be 2.5 and 3.5, respectively. Tenths were used in the computation of the median to permit comparisons.

Number of bedrooms.--Only rooms intended primarily to be slept in were counted as bedrooms. A bed-living room or a den intended primarily for purposes other than sleeping was not counted as a bedroom. A 1-room apartment, therefore, was reported as having no bedroom. Also, space which could be made into bedrooms (the upper floor of a 1-story house, for example) was not counted as a bedroom unless it was finished off and suitable for use as living quarters.

Number of dwelling units in structure.--A structure either stands by itself or has vertical walls dividing it from all other structures. The count of dwelling units in a structure is the total number of units in the structure, including both occupied and vacant units. A structure may be detached, attached, or semi detached. A detached structure has open space on all four sides; is an attached structure one of a row of three or more ad joining structures, or is a structure attached to a nonresidential structure; while a semi detached structure is one of two ad joining residential structures, each with open space on the remaining three sides. In apartment developments, each building with open space on all sides is considered a separate structure.

The statistics reflect the number of vacant dwelling units classified by the number of dwelling units in the structure in which they are located, rather than on the number of residential structures that contain vacant units.

In the 1955 survey, data were obtained on the number of dwelling units in the structure, regardless of the type of structure (detached, attached,

or semidetached) in which the unit was located. In the 1950 Census, statistics for 1- and 2-dwellingunit structures were compiled by type of structure as well as by number of dwelling units in the structure.

Duration of vacancy.--The length of time a dwelling unit was vacant was computed from the day the unit became vacant until the day of enumeration. It should be noted that the time period is not the total time a unit remains unoccupied nor the time a unit has been in a particular vacancy status, but it is the duration of vacancy up to the day of enumeration. For newly constructed units, it represents the time period since the date when the unit was considered a vacancy, that is, when construction had reached the point that all exterior windows and doors were installed and final usable floors were in place.

The time intervals used in the tables represent full months, calculated from a date in the month to the same date the following months. For example, if the unit became vacant on September 29 and was still vacant on the day of enumeration, November 17, the time reported would be "1 to 2 months," meaning that the unit had been vacant for more than one month but less than two months. Or if the unit became vacant on October 25 and was still vacant on November 17, the time reported would be "less than 1 month."

Monthly rent.--The monthly rent is the amount asked for the unit at the time of enumeration, regardless of whether it is to include furniture, heating fuel, electricity, cooking fuel, water, or other services. If the amount of rent were to vary during the year, the rent reported was the monthly amount asked at the time of enumeration. The data on rent for this report are limited to nonfarm available vacant dwelling units for rent. Rent statistics are not provided for vacant farm dwelling units because of the difficulty of separating the rental for the dwelling unit from the rental for the entire farm unit.

The median monthly rent of the dwelling units is the rent which divides the series into two equal parts, one-half of the units with rents higher than the median and the other half with rents lower than the median. In the computation of the median, a continuous distribution was assumed; and the limits of the class intervals were assumed to stand at the midpoints of the 1-dollar interval between the end of one of the rent groups and the beginning of the next. For example, the limits of the interval designated $30 to $39 were assumed to be $29.50 and $39.50.

Inclusion of utilities in rent.--The utilities included in the inquiry were heat, light, cooking fuel, and water. The statistics reflect whether all or not all of these utilities are provided for in the amount of rent asked at the time of enumeration, not what could be provided for more or less rent. Data on the inclusion of utilities are limited to nonfarm available vacant units for rent.

Sale price of 1-dwelling-unit structures.--The sale price is the amount asked for the property, including the structure and its land. Value data are limited to vacant nonfarm units in 1-dwelling-unit structures, without business, and with only one dwelling unit included in the property. The statistics on sale price for this report are limited to nonfarm available vacant units for sale. Values for other available units for sale are not provided because they would reflect varying amounts for farm land, business uses, or for more than one dwelling unit in the property.

The median sale price of the dwelling units is the amount which divides the series into two equal parts, one-half of the units with prices higher than the median and the other half with prices lower than the median. The median was computed on the basis of more detailed tabulation groups than are shown in the tables and was rounded to the nearest hundred dollars.

ure of sampling variability. The chances are about 68 out of 100 that the difference due to sampling variability between an estimate and the figure that would have been obtained from a complete enumeration is less than the standard error. The chances are about 95 out of 100 that the difference is less than twice the standard error and about 99 out of 100 that it is less than 2 times the standard error.

The standard errors of a few of the more important statistics are shown below. To illustrate: the available vacancy rate for the United States for the quarter is estimated as 2.7 percent. According to the table below, the standard error of this estimate is about 0.1 percent. The chances are, therefore, about 68 out of 100 that a complete enumeration would have yielded an estimate between 2.6 and 2.8 percent.

Table B.--STANDARD ERROR OF AVAILABLE VACANCY RATES (Range of 68 chances out of 100)

SOURCE AND RELIABILITY OF DATA

The estimates for 1955 presented in this report are based on data obtained in connection with the monthly population sample survey of the Bureau of the Census. This sample is spread over 230 sample areas comprising 453 counties and independent cities. A total of 24,000 to 26,000 dwelling units and other living quarters were designated for the sample during each of the three months covered by the report. Of this total, 21,000 to 23,000 were occupied dwelling units; 2,000 were vacant dwelling units; and the remainder were units which, at the time of enumeration, had been converted to commercial use, had been demolished, etc., or were not living quarters within the scope of the survey. Detailed information was obtained for each vacant unit in the sample.

The data for 1950 are based on the returns of the 1950 Census of Housing, and represent the results of a complete enumeration.

Since the 1955 statistics presented in this report are based on a sample, they are subject to sampling variability and may be expected to differ from results that would have been obtained from a complete count in which identical enumeration techniques were employed. The standard error is a meas