FILE INFORMATION

 

 

Geographic Coverage

 

State codes are shown except for nine states which are collapsed into three groups. The three state groupings are as follows: Maine and Vermont; Iowa, North Dakota and South Dakota; and Alaska, Idaho, Montana, and Wyoming. The sample was not designed to produce state level estimates. State codes are primarily useful in relating a respondent's recipiency of benefits to welfare reform thresholds and policies which may vary from state to state.

 

Identification Number System/Match Key Variables

 

The SPD identification scheme uses match key variables designed to uniquely identify individuals, provide a means of linking data for the same individuals across files, and grouping individuals into households and families across files over time. The various components of the identification scheme are listed below:

 

SIPP Panel Number SIPP_PNL

Sample Unit Identification Number PP_ID

Entry ID PP_ENTRY

Person Number PP_PNUM

Address ID ADDIDE(2,3,4,7,8,9,0)

SIPP _PNL, PP_ID, ADDID IHHKEY(2,3,4,7,8,9,0)

 

 

File Match Keys

 

This file includes match keys to merge with SPD and 1992/1993 SIPP data. These match keys link data for each person between the 1992 and 1993 SIPP Panels, the 1997 SPD Bridge, the 1998 SPD file and the first longitudinal SPD file.

 

Use the following variables to match back at the person level:

 

SIPP Panel Number SIPP_PNL

Sample Unit Identification Number PP_ID

Person Number PP_PNUM

Entry ID PP_ENTRY

 

Use the following variables to match back at the household level:

 

SIPP Panel Number SIPP_PNL

Sample Unit Identification Number PP_ID

Address ID ADDIDE(2, 3, 4, 7, 8,9,0)

 

The SIPP panel number identifies the panel in which the respondent participated. The sample person should either have an entry of 1992 or 1993 for their panel number.

 

The sample unit identification number was created by scrambling together the Primary Sampling Unit, segment, and serial numbers used for Census Bureau administrative purposes. These identifiers are constructed in the same manner as the 1992 and 1993 SIPP panel files, to enable matching to these files. To uniquely identify a household, you must use the sample unit identification (ID) number, the address ID, and the SIPP panel number. The sample unit identification number, the address ID, and the SIPP panel number can be used to link all households back to the original household.

 

The entry ID represents the address of the person at the time he/she was first interviewed and does not change even if the person moves. It is used in conjunction with the person number to uniquely identify people within the sample unit. This variable is the number 011 for all original sample people. For additional sample people, this variable can be 011 or greater than 011 depending on the current address ID of the unit which the new sample person joined. For example, a person who moves into a household with an ADDIDE0 of 011 will receive an PP_ENTRY of 011. Whereas, a person who enters a household spawned in 2000 (ADDIDE0=141) will have a PP_ENTRY of 141.

 

The person numbers represent the wave the person entered the sample. Person numbers such as 0101 and 0102 are assigned in Wave 1 of the SIPP. Person numbers such as 0201 and 0202 are

assigned to people added to the roster in Wave 2 of the SIPP. People added to the roster in the 2000 SPD have person numbers 1401 and 1402 and following sequentially as needed. People added to the roster in the 1999 SPD have person numbers 1301 and 1302 and following sequentially as needed. People added to the roster in the 1998 SPD have person numbers 1201 and 1202 and following sequentially as needed. People added to the roster in the 1997 SPD Bridge have person numbers 1101 and 1102 and following sequentially as needed.

 

The address ID is a three digit code that identifies the various household addresses associated with the same sample unit identification number. The first two digits of the address ID code indicate the wave or year in which that address was first interviewed. The third digit sequentially numbers that split into multiple households and have the same address ID. The address ID code is 011 for all sample addresses that are the same as in Wave 1 of the 1992 and 1993 SIPP panels. As the SIPP sample people move to new addresses, new address ID codes are assigned. For example, any new address to which sample unit members moved during the 2000 SPD is numbered from 141 to 149.

 

Households are defined at each cross sectional time point in this file: 1992, 1993, 1994, 1997, 1998, 1999, and 2000. If you would like to look at the household configuration in any given year, use the IHHKEY variable appropriate for that year. For example, to look at 1999 household structure, use IHHKEY99. The IHHKEY variables are a concatenation of SIPP_PNL; PP_ID and ADDID for the specific year. For example, IHHKEY99 is SIPP_PNL; PP_ID and ADDIDE9.

 

 

 

File Structure

 

The file is a rectangular person-level file. Household and Family level variables are included on the record for every person in the household.

 

Edits

 

The second longitudinal file is a fully edited and imputed data set.

 

Topcoding of Variables

 

To protect against the possibility that a user may recognize the identity of a SPD respondent with a very high income, income from every source is topcoded so that no individual amounts above $100,000 are revealed. This topcode amount is consistent with the topcoding for the 1992 and 1993 SIPP panels. Other economic variables are topcoded at the 97 percentile level, meaning the top 3 percent of values are not disclosed. Variables that have been topcoded will have a "T" in the second to the right position. NOTE: Aggregate amounts (PTOTVLR, PERNVLR, etc.) use topcoded amounts as input.

 

We topcode age by bottom coding year of birth. For the Second Longitudinal SPD file no age will be older than 88.

 

Weighting

 

The SPD panel universe is initially represented by all of the original sample people from the SIPP Panels 1992 and 1993. Each and everyone of these original sample people has an initial weight. Due to nonresponse in both the SIPP and the SPD, and a sample cut in the SPD in 1998, the initial weights of the respondents are adjusted to significantly compensate for the bias. Through the weighting process, the SPD panel universe is represented by the original sample people who have positive weights. The SPD second longitudinal file is the same as the SPD first longitudinal file except that it also includes the data collected from the SPD 1999 and 2000. Thus, like the SPD first longitudinal file, only part of the original sample people from the SIPP Panels 1992 and 1993 are included on the second longitudinal file because the SPD Bridge sample did not include all of the original sample people. Namely, the SPD Bridge (1997) sample which is the starting sample for the SPD consists only of the sample households that were interviewed in the last interview waves of the SIPP Panels 1992 and 1993. Thus, for those original sample people who were not included on the SPD second longitudinal file, their characteristics needed for the weighting process are obtained from the cross‑sectional and longitudinal files of the SIPP Panels 1992 and 1993.

 

There are three weights provided for sample people on the SPD second longitudinal file. These three weights are referred to as the traditional longitudinal panel weight, the 1999 quasi‑longitudinal panel weight, and the 2000 quasi‑longitudinal panel weight.

 

 

 

 

The sample people who meet the following definition have a positive traditional longitudinal panel final weight:

 

1)                  Lived in a 1992/1993 SIPP panel household during Wave 1 interview.

2)                   Were interviewed (self, proxy, or imputed) in each and every reference month in SIPP.

3)                   Were interviewed (self, proxy, or imputed) in 1997 SPD Bridge and 1998, 1999, and 2000 SPD.

 

All the other sample people included on the file have zero traditional longitudinal panel final weights.

 

The sample people who meet the following definition have a positive 1999 quasi‑longitudinal panel final weight:

 

1) Lived in a 1992/1993 SIPP panel household during Wave 1 interview.

2) Were interviewed (self, proxy, or imputed) in each and every reference month in SIPP.

3) Were interviewed (self, proxy, or imputed) in 1997 SPD Bridge and 1999 SPD, but may have been or may not have been interviewed in either or both the 1998 and 2000 SPD.

 

All the other sample people included on the file have zero 1999 quasi‑longitudinal panel final weights.

 

The sample people who meet the following definition have a positive 2000 quasi‑longitudinal panel final weight:

 

1) Lived in a 1992/1993 SIPP panel household during Wave 1 interview.

2) Were interviewed (self, proxy, or imputed) in each and every reference month in SIPP.

3) Were interviewed (self, proxy, or imputed) in 1997 SPD Bridge and 2000 SPD, but may have been or may not have been interviewed in either or both the 1998 and 1999 SPD.

 

All other sample people included on the file have zero 2000 quasi‑longitudinal panel final weights.

 

To provide a means for estimating the annual or calendar characteristics of young children based on the data on the SPD second longitudinal file, the characteristics of the non‑original sample children born after Wave 1 of the SIPP Panels 1992 and 1993 must be also taken into account. To enable an accounting for the characteristics of these non‑original sample children in any annual estimates, positive weights are assigned to a cohort of these non‑original sample children. For each non‑original sample child aged eight and below in 2000 if originated from the SIPP Panel 1992, or aged seven and below in 2000 if originated from the SIPP Panel 1993, having a designated parent that is an original sample person with positive traditional longitudinal (1999 quasi‑longitudinal, 2000 quasi‑longitudinal) weight, then a positive weight is assigned to the child based on the procedure described in more detail below. The weights of these non‑original children together with the traditional longitudinal (1999 quasi‑longitudinal, 2000 quasi‑longitudinal) weights of the original sample adults and children enable the users to make annual estimates of young children=s characteristics. Thus, we refer to these three SPD longitudinal annual weights as the traditional longitudinal annual weight, the 1999 quasi‑longitudinal annual weight, and the 2000 quasi‑longitudinal annual weight which are derived from the tradition longitudinal panel final weight, the 1999 quasi‑longitudinal panel final weight, and the 2000 quasi‑longitudinal panel final weight, respectively.

 

The procedure used for calculating the three longitudinal panel final weights and the three corresponding longitudinal annual weights of the sample people on the second longitudinal file is briefly described in the eight steps provided below. Refer to section 4 (Glossary) of the Technical Documentation for definitions for the key terms used in the eight steps of weighting described below.

 

STEP 1 B March 1993 was chosen as the reference point in time (control date) for the SPD panel universe used for measuring the effect of the Welfare Reform. Namely, the SPD panel universe consists of persons (including children) residing in the United States households and persons living in group quarters in March 1993. (Note that persons living in military barracks and institutions, such as prisons and nursing homes, are excluded.) The SPD panel universe is represented by combining the SIPP Panels 1992 and 1993 into one sample. The effect of the Welfare Reform can be assessed based on the various longitudinal (time dependent) characteristics of the people in the SPD panel universe.

 

STEP 2 B An initial weight was assigned to each original sample person (including children). An original sample person is a person who at the time of the SIPP Wave 1 interview resided in an interviewed sample household or group quarters. The inverse of this initial weight represents the probability of an original sample person residing in an interviewed Wave 1 sample household in either the SIPP Panel 1992 or 1993, depending on which SIPP panel he/she originally belonged.

 

Every sample person who was not an original sample person was assigned an SPD traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal panel final weights of zero.

 

For sample children aged eight or less if spawned from the SIPP Panel 1992 and aged seven or less if spawned from the SIPP Panel 1993 (as of March 2000) who was not an original sample person, they are assigned annual weights according to the procedure provided in Step 8. Note that this group of non‑original sample persons nominally represents the children born after the inception of the SPD panel universe.

 

STEP 3 B Since each of the SIPP Panels 1992 and 1993 (samples) was a nationally representative sample by itself and their sample sizes are approximately the same, combining them into one sample reduces the weight of each panel sample person by half.

 

STEP 4 B Original sample persons were then divided into two cohorts as follows: the first cohort consists of the original sample persons who are qualified as longitudinally interviewed between Wave 1 of the SIPP Panels 1992 and 1993 up to the SPD Bridge. The second cohort consists of the original sample persons who are not qualified as longitudinally interviewed between Wave 1 of the SIPP Panels 1992 and 1993 up to the SPD Bridge. The first group is referred to as the SPD Bridge longitudinally interviewed. The second group is referred to as the SPD Bridge longitudinally non-interviewed.

 

 

The SPD Bridge non-interview adjustment served as a means of appropriately transferring the weights from the SPD Bridge longitudinally non-interviewed to the SPD Bridge longitudinally interviewed with similar demographic and economic characteristics ^[1] . Sample persons were classified based on the following variables: age, race, ethnicity, education, labor force status, employment status, income types, assets, and income level.

Every SPD Bridge longitudinally interviewed person was assigned a non‑interview adjustment factor to inflate their initial weights.

 

Every SPD Bridge longitudinally non-interviewed person was assigned a traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal panel final weight of zero, and excluded from further processing.

 

STEP 5 B Due to budget constraints, some sample household units were cut ^[2] in the SPD 1998. SPD Bridge longitudinally interviewed persons were divided into two cohorts. The first consists of those belonging to the sample households selected into the SPD 1998 sample, and we call this group Athe selected SPD Bridge longitudinally interviewed.@ Those belonging to the sample households not selected into SPD 1998 sample are called Athe not-selected SPD Bridge longitudinally interviewed.@

 

A sample cut factor was assigned to the selected group in accordance with the household demographic characteristics provided in the document referred to in Footnote 2. The adjustment served as a means to appropriately transfer the weights from the not-selected SPD Bridge longitudinally interviewed to the selected SPD Bridge longitudinally interviewed.

Every not-selected SPD Bridge longitudinally interviewed person was assigned an SPD traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal panel final weight of zero and excluded from further processing.

 

STEP 6 B For each of the three panel weights, the selected SPD Bridge longitudinally interviewed persons were divided into two cohorts.

 

For each panel weight, the first cohort consists of the selected SPD Bridge longitudinally interviewed persons who do qualify as interviewed. The second cohort consists of the selected SPD Bridge longitudinally interviewed persons who do not qualify as interviewed. A list of requirements that must be met to qualify as interviewed for each of the panel weights was given earlier in the weighting section.

 

For each panel weight (traditional, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal), a second non‑interview adjustment procedure was independently performed in the same manner as the first non‑interview adjustment in Step 4. Namely, this second adjustment served as a means

to appropriately transfer the weights from the non‑interviewed to the interviewed with similar demographic and economic characteristics as classified in Step 4.

 

For each panel weight, those people who qualify as interviewed were assigned a second non‑interview adjustment factor to inflate their weights.

 

For each panel weight, those people who qualify as non‑interviewed were assigned a weight of zero and excluded from further processing.

 

STEP 7 B A ratio adjustment procedure was independently performed to finish each panel weight (traditional, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal). The ratio adjustment procedure involved raking to match a set of SPD population estimates with a corresponding set of control (benchmark) population estimates at a representative control date. The control population estimates were available for the classifications based on the following demographic variables: age, sex, race, ethnicity, householder living with or not living with relative, non-householder related to or not related to householder. As described in Step 1, the representative control date for the SPD panel universe was March 1993. The control population estimates are from the CPS population estimates produced for March 1993. The ratio adjustment procedure served as a means to improve the population coverage of the SPD sample. The classification of the sample persons into groups for the ratio adjustment also served as a post-sampling stratification. Therefore, as a byproduct of the ratio adjustment, the variance estimates of the estimates based on the SPD sample are generally improved as well.

 

The three sets of positive weights obtained after the ratio adjustment were the final weights for the SPD traditional longitudinal panel interviewed persons, the 1999 quasi‑longitudinal panel interviewed persons, and the 2000 quasi‑longitudinal panel interviewed persons.

 

STEP 8 B Creation of the traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal annual weights was done in two parts. For the first part, all sample people except the non‑original young sample children, the traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal annual weights were set equal to their traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal panel final weights, respectively.

 

For the second part, each non‑original young sample child (eight or less) whose designated parent is an original sample person, three intermediate weights were created by giving them their designated parent=s traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal annual weights, respectively.

 

Each of the three intermediate weights of these weighted non‑original children was independently adjusted by ratio adjusting their weighted totals to various controls (classified by sex, race, and ethnicity) for June 2000. Once the ratio adjustment factors were applied to the intermediate weights, these non‑original children were assigned their final traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal annual weights. Their application is described in the next section (see below).

 

Longitudinal Weight Associated with Non-original Sample Children

 

The traditional longitudinal, 1999 quasi‑longitudinal, and 2000 quasi‑longitudinal annual weights are for calculating annual or calendar year estimates.

 

The traditional longitudinal annual weight is positive only for original sample people who provided a self or proxy, or whose data were imputed, in each and every reference month for SIPP, SPD 1997 Bridge, SPD 1998, SPD 1999, and SPD 2000, and for non‑original sample children (aged eight or less) born after the SIPP 1992/1993 Wave 1 interview whose designated parents are original sample people and have positive traditional longitudinal annual weight.

 

The 1999 quasi‑longitudinal annual weight is positive only for original sample people who provided a self or proxy, or whose data were imputed, in each and every reference month for SIPP, SPD 1997 Bridge, and SPD 1999, and for non‑original sample children (aged eight or less) born after the SIPP 1992/1993 Wave 1 interview whose designated parents are original sample people and have a positive 1999 quasi‑longitudinal annual weight.

 

The 2000 quasi‑longitudinal annual weight is positive only for original sample people who provided a self or proxy, or whose data were imputed, in each and every reference month for SIPP, SPD 1997 Bridge, and SPD 2000, and for non‑original sample children (aged eight or less) born after the SIPP 1992/1993 Wave 1 interview whose designated parents are original sample people and have a positive 2000 quasi‑longitudinal annual weight.

 

The annual weights of the weighted non-original sample children together with the annual weights of the original sample adults and children associated with the traditional longitudinal (1999 quasi-longitudinal, 2000 quasi-longitudinal) panel weight enable the users to make annual estimates of young children=s characteristics. When calculating an annual estimate of a characteristic of young children, the portion of the estimate contributed by the weighted non-original sample children must be calculated based only on the weighted non-original sample children born in or prior to the calendar year under consideration. The non-original sample children weights, for those aged eight or less, are intended only to approximate growth in the universe. Some caution should be given when interpreting results for children aged 8 or less. The annual estimates of the characteristics of these children for a calendar year closer to 2000 are likely to be more accurate than those for a calendar year further away from 2000. This is because all three types of annual weights for these children were adjusted to improve the population coverages for June 2000.

 

Estimation of Person Characteristics

 

Some basic types of longitudinal estimates that can be constructed using the longitudinal weight are described below in terms of estimated numbers. Of course, more complex estimates, such as percents, averages, and ratios can be constructed from the estimated numbers. The SPD longitudinal weights can be used to construct the following types of longitudinal estimates:

 

1. The number of people who have ever experienced a characteristic or situation during a given time. (For example, the number of people who experience unemployment during

 

1999.) To construct such an estimate, sum the weights over all people who possessed the characteristic of interest at some point during the time period of interest.

 

2. The amount of a characteristic accumulated by people during a given time. (For example, the amount of unemployment compensation received by unemployed people during 1999.) To construct such an estimate, compute the product of the weight times the amount of the characteristic and sum this product over all appropriate people.

 

Longitudinal Research Using This File

 

The SPD is designed exclusively to support longitudinal analysis of the impact of welfare reform. The Second Longitudinal SPD data can be linked to the 1992 and 1993 SIPP Panel and Cross-sectional files, the 1997 SPD Bridge, the 1998 SPD file and the First Longitudinal SPD file using the following variables:

 

SIPP Panel Number SIPP_PNL

Sample Unit Identification Number PP_ID

Entry ID PP_ENTRY

Person Number PP_PNUM

Address ID ADDIDE(2,3,4,7,8,9,0)

 

A Longitudinal weight is assigned to 100-level persons with full panel weights in the 1992/1993 SIPP file who were successfully interviewed in 2000. Note the full panel weights on the SIPP files were assigned to 100-level people who were interviewed for the entire time they remained in the SIPP universe or who had at most 1 missing interview bounded by successful interviews.

 

The SPD data represent the behavior and characteristics of people in two fixed cohorts. One cohort represents the population as it existed in March 1992 from the 1992 panel of the SIPP and the other population as of March 1993 from the 1993 panel. This is not a traditional longitudinal survey in that it does not repeat the same measure throughout the period. Each round of the SPD interviewing, beginning with the Bridge in 1997, does not represent cross-sectional snapshots of the U.S. population. It does offer insight into what the current condition is of the people in the U. S. population in the early 1990s just prior to welfare reform.

 

The core information common throughout the data collection (although reference periods and question phrasing vary) consists of basic demographics, labor force activity, income, and program participation. The longitudinal file consists of data collected using three different instruments, each with variations in wording and context.

 

Obtaining Access to SAQ Data

 

The SAQ data (adult and adolescent) will only be available through the Census Bureau=s Research Data Centers. Contact the Research Data Center staff for the requirements for reviewing the SAQ data.