Identifying

To uniquely identify a person in the core wave files, analysts should employ the three variables shown in Table 10-2. Users should note that in the 1996 Panel, the entry address ID is no longer needed for unique identification. Its continued use will not create any problems; it is simply redundant information. That is a change from earlier panels in which the entry address ID was key to uniquely identifying persons.

The variables in Table 10-2 have the following characteristics:

• SSUID (SUID) uniquely identifies each initially sampled dwelling unit.⁶ Every person in a core wave file was either a member of one of those units (an original sample member) or lives with someone who was a member of an initially sampled dwelling unit. A person’s connection to that unit is an attribute of that person and does not change over time.⁷ This means that as people move from address to address, their SSUID (SUID) stays the same. As new people join the homes of original sample members, they receive the SSUID (SUID) of the original sample members.
• EENTAID (ENTRY) identifies the address where the person lived at the time she or he was first interviewed. It does not change even if the person moves.8 Prior to the 1996 Panel, it was used in conjunction with the person number and sample unit ID to uniquely identify persons within the sampling unit. It is not needed to uniquely identify persons in the 1996 panel. Values for this variable are unique only within sample units. The entry address ID has two components. The first part of the ID number (two digits in the 1992 and 1996 Panels, and one digit in all others) identifies the wave in which SIPP interviews were first conducted at the address. The second part of the number (one digit in all panels) sequentially numbers addresses within a sample unit [SSUID (SUID)] that enter the sample in the same wave. See Chapter 9 for a more complete discussion.
• Prior to the 1996 Panel, PNUM uniquely identified a person within the sample unit and entry address ID. In the 1996 Panel, EPPPNUM uniquely identifies a person within the sample unit. EPPPNUM (PNUM) does not change even if the person moves.9 The first part of EPPPNUM (PNUM) (two digits in the 1992 and 1996 Panels, one digit in all others) indicates the wave in which the person was first interviewed.10 The remaining two digits are sequentially assigned within the household. Thus, original sample members are assigned person numbers ranging from 100 to 199. Individuals who enter the SIPP sample in Wave 2 are assigned a person number ranging from 200 to 299. Those who enter in Wave 10 are assigned person numbers ranging from 1001 to 1099.

Table 10-3 illustrates how the combination of SSUID (SUID), EENTAID (ENTRY), and EPPPNUM (PNUM) uniquely identifies people and provides information about when they first entered the SIPP sample. In this example, there are eight individuals: five are original sample members, one person joined the SIPP sample in Wave 3, one joined in Wave 4, and another joined in Wave 7. Note that the person who joined the sample in Wave 3 (pre-1996 Panel) was assigned a person number of 301, but an entry address ID of 21 (not 31). That is because the first part of the entry address ID indicates the wave in which that address was first occupied by any SIPP sample member, which is not necessarily the wave in which a given member entered the sample.

Identifying Households

The term household, as used in Census Bureau publications, refers to a group of persons who occupy a housing unit. A house, an apartment or other group of rooms, or a single room is regarded as a housing unit if it is occupied or intended for occupancy as separate living quarters. That is, the occupants do not live and eat with any other persons in the structure and there is direct access from the outside or through a common hall. A group of friends sharing an apartment constitutes a household. Noninstitutional group quarters, such as rooming and boarding houses, college dormitories, convents, and monasteries, are classified as group quarters rather than households.

To uniquely identify a household or group quarters in the core wave files, analysts should use the two variables shown in Table 10-4.

People with the same SSUID (SUID) and SHHADID (ADDID) values live in the same household (or group quarters). The six individuals in Table 10-5 make up three households. The first household contains the first four individuals. The second household contains one person. The third household contains one person.

Each household contains one reference person. The household reference person is the person in whose name the home is owned or rented. If the house is owned or rented jointly by more than one person (such as a married couple or some roommate situations), any of those people may be listed as the "reference person." Users may find it helpful to refer to Figure 2-1 (pp. 2-10-2-14), which illustrates the concepts of household and changes in household composition.

Identifying Families

The term family, as used in Census Bureau publications, refers to a group of two or more people related by birth, marriage, or adoption who reside together; all such individuals are considered members of one family.

There are several types of families that the Census Bureau distinguishes:

• A primary family is a family containing the household reference person and all of his or her relatives. This means that a household composed of a husband and wife, their son, and their son’s wife (i.e., the daughter-in-law) is classified as a primary family containing four people.
• A related subfamily is a nuclear family that is related to but does not include the household reference person. For example, the son and his wife (i.e., the daughter-in-law) in the preceding example are a related subfamily.
• An unrelated subfamily (sometimes called a secondary family) is a nuclear family that is not related to the household reference person. Thus, a husband and wife who live in a friend’s house are classified as an unrelated subfamily. A mother and daughter who live in the mother’s boyfriend’s apartment are classified as an unrelated subfamily.
• A primary individual is a household reference person who lives alone or lives with only nonrelatives. Primary individuals are sometimes treated by the Census Bureau as families with only one person and are referred to as pseudo-families.
• A secondary individual is not a household reference person and is not related to any other people in the household. Secondary individuals are sometimes treated by the Census Bureau as families with only one person and are referred to as pseudo-families.

To uniquely identify a family, analysts should use the variables shown in Table 10-6.

The Census Bureau has two principal methods for distinguishing families.

__________
^a EFTYPE = 1 means the person belongs to a primary family (including related subfamily members). EFTYPE = 3 means the person belongs to an unrelated subfamily. EFTYPE = 4 means the person is a primary individual. EFTYPE = 5 means the person is a secondary individual.

^b FAMTYP = 1 means the person belongs to a primary family (including related subfamily members). FAMTYP = 3 means the person belongs to an unrelated subfamily. FAMTYP = 4 means the person is a primary individual. FAMTYP = 5 means the person is a secondary individual.

__________
³ Although an attempt was made in the 1996 Panel to give all variables meaningful names, the eight-character limitation imposed by many software packages places severe constraints on the degree to which this can be done. Prior to the 1996 Panel, the situation was more pronounced since numeric sequencing was used to name variables (e.g., in the paper survey, SE22318 is the variable that indicates the total number of employees working for the second business; in CAI, that variable is TEMPB2). In the 1996 Panel, variable names beginning with a "T" have been topcoded to protect respondent confidentiality.
⁴ The universe definitions included in the data dictionaries prior to the 1996 Panel were not always accurate. Users of pre-1996 SIPP Panels should check the skip patterns in the actual survey questionnaire to determine which subset of respondents was asked each question.
⁵ Prior to the 1990 Panel, core wave files had one record per person. Each record contained four occurrences of each monthly variable. For more information, see earlier editions of the SIPP Users’ Guide.
⁶ The SSUID (SUID) is a random recode of three other variables in the Census Bureau’s internal (not public use) files: the respondent’s sampling area (PSU), the cluster of housing units within that area (called the "segment"), and a sequentially assigned serial number. Those variables are omitted from the public use files to protect the confidentiality of the respondents.
⁷ There is one rare exception to this rule for Panels prior to 1996, which is described in the section entitled "Identifying Movers" later in this chapter.
8 See footnote 6.
⁹ See footnote 6.
¹⁰ For Wave 10 of the 1992 Panel and for the 1996 Panel, the first two digits of PNUM instead of the first digit identify the wave in which the person entered sample.

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