The Future of the Survey of Income and Program Participation (1993) / Chapter Skim
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6 DATA PRODUCTS AND THEIR USE
6 DATA PRODUCTS AND THEIR USE
Pages 158-201
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From page 158... ...
Such publications, containing basic descriptive statistics plus key analytic measures (e.g., spell lengths for program participation) , are a valuable reference source for the general userand their value increases as each successive report adds to a time series.
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From page 159... ...
To date, the publication program for SIPP, while including many useful reports, has not adequately served these needs. A Checkered History The Census Bureau's publication program for SIPP has been very uneven, including a stretch of several years in which almost nothing was published from the core information on income and program participation (see Table 6-1 for a chronological list of SIPP report titles published through 1991~.
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From page 160... ...
from Major Assistance Programs Aug. 1989 Transitions in Income and Poverty Status: 1984 panel file (P-70-l5)
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From page 161... ...
Waves 1-7, 1986-1987, 1985 panel file June 1990 Transitions in Income and Poverty Status: 1985 panel file (P-70- 18)
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From page 162... ...
by race and edacity of householder, metropolitan residence, region, household type, age of householder, and work disability status of householder; · mean monthly household cash income, and household receipt of unemployment compensation, cash benefits, food stamps, and other noncash benefits by charactensucs (as listed immediately above) ; · household receipt of food stamps, WIC, free or reduced-pnce school meals, public or subsidized housing, Medicaid, Medicare, AFDC or other cash assistance, SSI, social security, veterans' benefits, and unemployment compensation by household type crossed by household receipt of food stamps, etc.
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From page 163... ...
Reports from the 1984 panel file included characteristics of persons receiving benefits from major assistance programs, transitions in income and poverty status for 1984-1985, spells of job search and layoff, and the effects of family disruption and economic hardship on children. Reports from the 1985 panel file included transitions in health insurance coverage (this report also used the core data Tom several SIPP panels to provide quarterly estimates of health insurance coverage for 1986-1988)
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From page 164... ...
Updated crosssectional statistics will be published in 1993 on income, poverty status, and programs, followed by publication in 1994 of updated longitudinal statistics on transitions in income, poverty, and program participation from the 1990 panel.2 Thereafter, cross-sectional and longitudinal reports will alternate yearly. In addition, the Census Bureau plans to prepare a major report that compares annual income and poverty data from the 1990 SIPP panel with data from the March 1991 CPS.
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From page 165... ...
Special studies could cover both substantive and methodological subjects-such as an analysis of trends in income and poverty status for particular subgroups of the population and an investigation of new methods of estimating duration of spells of program participation-and would go well beyond the level of analysis provided in the descriptive reports. Such studies would of course draw heavily on SIPP but should also include relevant data, as appropriate, from such sources as the March CPS income supplement, other surveys, and administrative records.
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From page 166... ...
Reports on Demographic and Employment Transitions SIPP is a rich source of information on a wide range of topics other than income and program participation. As we have noted, the Census Bureau has prepared a number of interesting and valuable publications from various SIPP topical modules.
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From page 167... ...
Recommendations A strong publication program on income, program participation, and related topics is an essential component of the Census Bureau's responsibilities for SIPP. The program should include several types of descriptive and analytical report series that provide basic information and more in-depth analysis from the survey.
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From page 168... ...
should be published; cross-sectional statistics should also be issued on a frequent schedule. The Census Bureau should also establish a research report series to include in-depth analytical and methodological studies of special topics related to income and program participation.
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From page 169... ...
Members of the panel wrestled with these problems in working on illustrative tabulations for SIPP reports on income, poverty, and program participation (for details see Citro, 1990, 199Ib) .5 Here we provide an overview of some of the more important conceptual and measurement issues that will have to be considered in developing core statistics from SIPP, particularly those that involve use of the SIPP longitudinal data: relating statistics to policy concerns; specifying analysis units (e.g., persons, fa~lies)
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From page 170... ...
Nonetheless, it is important that SIPP statistics on income and program participation take into account important policy concerns and perspectives. Indeed, the detail in SIPP makes it possible to provide a rich set of policy-relevant statistics, for which we have several concrete suggestions.
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From page 171... ...
SIPP also obtains detailed inflation on assistance programs, including the timing of benefit receipt, so that concurrent versus sequential multiple program participation can be distinguished. We recommend that many more categories of programs be distinguished in published statistics than was done in the first SIPP report on participation in major assistance programs (P-70, No.
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From page 172... ...
Here we note our support for a published series of alternative measures of income from SIPP- like the series published from the March CPS that take account of taxes and noncash benefits. Units of Analysis The Census Bureau's P-60 reports, based on the March CPS, provide crosssectional statistics for different units of analysis, including annual income for household and family units, personal income for people aged 15 and older, and poverty status for families and people (based on family income and poverty thresholds)
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From page 173... ...
For cross-sectional statistics, one can use the monthly data from SIPP directly to construct annual (or quarterly) average monthly income and program participation measures by treating each month as a separate crosssection that is weighted to represent the total population and then taking an average (as was done in the quarterly reports from the 1984 SIPP panel.
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From page 174... ...
A month appears to be too short a period in which to establish economic hardship, given measurement error and the fact that many people experience fluctuations in income that may put them below the poverty line for a short time but not over a longer period.~3 For longitudinal statistics, the use of the detailed income and family composition data in SIPP to develop longitudinal income measures for units that are observed over a period longer than a month (e.g., measures of change in income level and poverty or program participation status from one year to the next) is more problematic.
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From page 175... ...
found from analysis of the 1984 SIPP panel that the specifics of a longitudinal household definition had relatively little effect on annual poverty rates, but only if part-year units were time weighted (e.g., a unit that existed for only 7 months would be given a weight of 7112~. Not using time weights increased the poverty rate because part-year units had considerably higher poverty rates than full-year units under all definitions More important, the amount of the increase varied because the number of part-year units and their poverty rate varied across definitions.~4 It is not a desirable property of a measurement concept that minor variations in specification produce important differences in results.
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From page 176... ...
Contextual Variables The use of SIPP monthly data makes it possible to develop longitudinal measures of income, poverty, and program participation that properly reflect each person's economic status over the measurement period. However, during that period whether it be a fixed calendar unit such as 1 or 2 years, the length of a SIPP panel, or the length of a spell of poverty or program participation-many people will have experienced other changes that represent important contextual variables.
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From page 177... ...
Yet that distinction is important given the strong evidence that changes in marital status, employment status, and other characteristics relate to changes in income and program participation (see e.g., Ruggles and Williams, 1987; Williams and Ruggles, 1987~. However, it can be difficult to develop indicators of change in contextual variables that do not overwhelm users with detail given the many different patterns that are possible for example, during a year, some people may experience several employment or marital status changes of different types.
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From page 178... ...
The detail is justified given that one can legitimately seek to identify causal relationships from tables of spell duration and other characteristics for people who enter or exit poverty and programs. Using the marital status example, we suggest the following approach for categorizing contextual variables in tables of poverty or program participation spells, entrances, and exits.
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From page 179... ...
4) offers a critique of the poverty measure's equivalence scale, particularly of the lower poverty thresholds for families headed by art elderly person compared with other families and the irregular patterns of increase in the thresholds by family size.
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From page 180... ...
income-to-poverty ratio category. We support the desirability of research into alternative methods of constructing an appropriate equivalence scale for the official poverty measure, but we focus here on the short-te~ question of what type of equivalence scale to use in SIPP publications at this juncture and for what purposes.20 SIPP core publications, like those from the March CPS, will include tabulations of the distribution of family income for people unadjusted for family composition.
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From page 181... ...
Analysis of Spells Over the past decade, there has been growing policy and research interest in such questions as the extent to which program beneficiaries are dependent on assistance over the long term versus those needing help only for short periods.22 Paralleling this interest has been further development of the needed research tools that make it possible to analyze spells and duration of poverty and program participation namely, large-scale longitudinal data sets, powerful computer hardware and software, and statistical methods for estimating spell duration. The SIPP longitudinal data have already been used by analysts to estimate duration of spells of low income, spells of participation in AFDC and food stamps, and spells without health insurance coverage (see Chapter 1; see also Gogan, 1988~.
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From page 182... ...
notes, survival analysis of this type is a popular approach for analyzing spell durations and their determinants, and we support its use to develop estimates of spells of low income and program participation for inclusion in SIPP published reports. We propose that these reports contain tables that show the median estimated spell length and the survival rate or percentage of spells in progress after 1, 4, 8, 12, 16 months, etc., derived from the product-limit (Kaplan-Meter)
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From page 183... ...
One possibility is to base the analysis on original sample persons in a panel file who provide data for every wave for which they are eligible, making use of the longitudinal weights in the analysis.25 With this approach, nght-censonug occurs when a spell is still in existence at the end of the panel or when a panel member leaves the survey universe through death, institutionalization, or emigration. The former type of nght-censoring, which is independent of the spell duration, is routinely handled by survival analysis techniques.
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From page 184... ...
These spells are a length-biased sample of spells since longer spells are more likely to be present at any particular date One way to include such spells is to define the spell population to include all spells that begin in a period that began prior to the start of the survey for example, in the case of 1990 SIPP panel, one might seek to estimate the duration of all spells of low income that began in the period January 1986 to December 1990 (or 1991~. The beginning date is chosen under the assumption that all of the spells existing at the start of the panel commenced after that beginning date.
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From page 185... ...
SIPP makes it possible to identify spells as short as 1 month; however, it may not always be sensible to do so for published spell analyses of low income and program participation. For duration estimates for low income, a primary concern of analysts has to do with the persistence of poverty over time.
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From page 186... ...
For program participation, it is appropriate to include short spells of recipiency, provided that they are measured accurately.27 However, because analysts are concerned with the persistence of welfare dependency, it could be misleading to recognize very short breaks in recipiency. For example, administrative actions (e.g., recertification)
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From page 187... ...
The longitudinal panel files include up to three weights for each record: a weight for people with complete data for the first calendar year covered by the panel; a weight for people with complete data for the second calendar year; and a panel weight for people with complete data for all 32 months.30 Records for other people who participated in the survey are also includedso that their information can be used ire analysis of the weighted cases but are not assigned weights. We see no problem in principle in the case of average monthly crosssectional statistics from SIPP, which can readily make use of the monthly weights and thereby include the maximum number of observations.3~ For tables of annual income that are designed for comparability with the March CPS, we suggest using the cross-sectional weights for December of the income year.
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From page 188... ...
Tables that present duration estimates and other information related to spells of low income and program participation can make use of the longitudinal panel weights. However, to date, most spell analyses conducted with the 1984 SIPP panel (e.g., Ruggles, 1989; Ruggles and Williams, 1989; McBride and Swartz, 1990)
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From page 189... ...
MICRODATA PRODUCTS Timely release of computer-readable files containing microdata (i.e., the coded values for the information furnished by individual respondents, suitably processed to protect the confidentiality of the replies) is as important a component of the data dissemination program for a rich, complex survey like SIPP as the regular release of publications.
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From page 190... ...
This problem was even more pronounced for the longitudinal panel files (see below) , which each required three, four, or five tapes.
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From page 191... ...
Initially, a 12-month file was developed from the 1984 panel, followed by a 32-month panel file. The longitudinal files include only information from the core questionnaire; users must merge topical module data from separate files Working with input from users (see, e.g., Smith, 1989)
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From page 192... ...
Timing Although the Census Bureau has made commendable progress in improving delivery schedules for SIPP microdata files, we believe that further improvements in timeliness are both necessary and feasible. In order to achieve the goal of SIPP's serving as the nation's main source of income statistics, core data files must be available from SIPP on about as timely a basis as they are from the March CPS income supplement~urrently about 6 months ence with the person-month format and consider ways to alleviate problems that arise.
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From page 193... ...
Kinds of Files Currently, the Census Bureau releases wave and panel files from each panel of SIPP (separate wave files for core and topical module information)
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From page 194... ...
. Also, some programrelated variables for which the Food and Nutntion Service provided funding to include on the initial 12-month longitudinal file from the 1984 panel were never adopted for the 32-month panel files.
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From page 195... ...
Priority improvements include: · moving toward ~ goal of releasing core data files within 6 months after the end of data collection; · producing calendar-year files that combine panels, in addition to wave and panel files; · determining, in consultation with users, changes and additions to the file contents that would assist their analyses; and · developing additional ways of delivering SIPP microdata products to users, such as by means of high-storage capacity compact disks (CD-ROM) and an improved on-line data extraction system.
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From page 196... ...
Codebooks are available in printed form and as machine-readable files attached to the data files. A SIPP Users' Guide containing additional explanatory information for users about SIPP and its microdata products was initiated at the start of the survey but took several years to prepare the first edition was released in 1987 (Bureau of the Census, 1987~.
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From page 197... ...
Census Bureau staff further encouraged SIPP researchers to apply for ASA/Census fellowships to use the data files on-site at the Bureau. In addition, Bureau staff regularly appeared at the monthly meetings of SIPP analysts in the Wash 41Arrangements for the APDU SIPP supplement and for an APDU SIPP committee to consult with the Census Bureau about the SIPP data products and documentation were made in early l9g9.
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From page 198... ...
Recommendation We urge the Census Bureau to continue regular consultations with users about needed kinds of documentation and other informational and instructional matenals. We cannot stress enough the importance of having comprehensive, accurate, and intelligible documentation and related services to interest users in the potential of SIPP data and to enable them to make the most cost-effective use of the data.
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From page 199... ...
The published research report series that we recommend above will also play a valuable role in this regard.45 Preparation of a complete on-line bibl~ogra 44Work is in progress under a joint statistical agreement between the Census Bureau and the University of Michigan to develop documentation for the longitudinal imputations in the SIPP panel files, and the Census Bureau expects to make arrangements with another organization to obtain documentation for the cross-sectional imputations and edits. Also, work is in progress by Social and Scientific Systems, Inc., under contract to the Census Bureau, to develop documentation for recoded vanables.
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From page 200... ...
The upcoming redesign of SIPP, which will entail changes in data products and documentation, makes it all the more important to have good means of communication with individual users and the user community as a whole. Recommendation 6-4: The Census Bureau should work to improve documentation and related user information services for SIPP.
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From page 201... ...
~ =~1~1aluing e~ct1ve channels of communication For users to Wed back problems and suggesdous and learn of the Bureaus response, and for users to be indeed of new development in the survey and as data product 207
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