National Incidence Studies of Missing, Abducted, Runaway, and Thrownaway Children (NISMART), 1999 (ICPSR 4566)
Alternate Title: NISMART-2
Principal Investigator(s): Hammer, Heather, Temple University. Institute for Survey Research; Sedlak, Andrea J., Westat, Inc.; Finkelhor, David, University of New Hampshire. Crimes Against Children Research Center
The National Incidence Studies of Missing, Abducted, Runaway, and Thrownaway Children (NISMART) were undertaken in response to the mandate of the 1984 Missing Children's Assistance Act (Pub.L. 98-473) that requires the Office of Juvenile Justice and Delinquency Prevention (OJJDP) to conduct periodic national incidence studies to determine the actual number of children reported missing and the number of missing children who are recovered for a given year. The first such study, NISMART-1 (NATIONAL INCIDENCE STUDIES OF MISSING, ABDUCTED, RUNAWAY, AND THROWNAWAY CHILDREN (NISMART), 1988 [ICPSR 9682]), was conducted from 1988 to 1989 and addressed this mandate by defining major types of missing child episodes and estimating the number of children who experienced missing child episodes of each type in 1988. At that time, the lack of a standardized definition of a "missing child" made it impossible to provide a single estimate of missing children. As a result, one of the primary goals of NISMART-2 was to develop a standardized definition and provide unified estimates of the number of missing children in the United States. Both NISMART-1 and NISMART-2 comprise several component datasets designed to provide a comprehensive picture of the population of children who experienced qualifying episodes, with each component focusing on a different aspect of the missing child population. The Household Survey -- Youth Data and the Household Survey -- Adult Data (Parts 1-2) are similar but separate surveys, one administered to the adult primary caretaker of the children in the sampled household and the other to a randomly selected household youth aged 10 through 18 at the time of interview. The Juvenile Facilities Data on Runaways (Part 3) sought to estimate the number of runaways from juvenile residential facilities in order to supplement the household survey estimate of the number of runaways from households. And the Law Enforcement Study Data, by case perpetrator, and victim, (Parts 4-6) intended to estimate the number of children who were victims of stereotypical kidnappings and to obtain a sample of these cases for in-depth study.
These data are freely available.
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Hammer, Heather, Andrea J. Sedlak, and David Finkelhor. NATIONAL INCIDENCE STUDIES OF MISSING, ABDUCTED, RUNAWAY, AND THROWNAWAY CHILDREN (NISMART), 1999. 2007. ICPSR04566-v1. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [producer and distributor], 2007-07-19. http://doi.org/10.3886/ICPSR04566.v1
Persistent URL: http://doi.org/10.3886/ICPSR04566.v1
This study was funded by:
- United States Department of Justice. Office of Justice Programs. Office of Juvenile Justice and Delinquency Prevention (1995-MC-CX-K004)
Scope of Study
Geographic Coverage: United States
Date of Collection:
Unit of Observation: Parts 1-3: Youth, Parts 4-6: Victim, perpetrator, and case
Universe: Parts 1-2: Households with at least one child aged 18 or younger who had lived in the house for two consecutive weeks in the 12 months prior to screening. Part 3: All group homes, juvenile detention centers, residential treatment centers, and runaway and homeless youth shelters serving the selected counties. Parts 4-6: All law enforcement agencies serving the selected counties.
Data Types: survey data
Sample: Parts 1-2: A list-assisted RDD (Random Digit Dial) methodology was used to select a nationally representative sample of telephone households from the GENESYS Sampling System frame. Typically, a list-assisted RDD design is a one-stage random selection process resulting in equal probabilities of selection (EPSEM) design and no clustering, with each household treated as a Primary Sampling Unit (PSU). A detailed description of the sampling design is in HOUSEHOLD SURVEY METHODS TECHNICAL REPORT which is included in this data collection. Part 3: A stratified, two-stage sample design was applied. In the first stage, 30 Primary Sampling Units (PSUs) were sampled from a listing of the national universe of counties and groups of small, adjacent counties. The PSUs were selected with probability proportionate to the number of children (aged 0 to 17) according to the 1990 Census. Within the 30 PSUs, a total of 922 eligible facilities were identified. This frame was stratified by type of facility, and 75 facilities were sampled with probability proportionate to size (PPS), using weighted capacity as the measure of size. Parts 4-6: Nationally representative sample of 400 counties. Counties were selected with probabilities proportional to size.
Weight: Parts 1-2: Survey weights were developed to compensate for the higher probability of selection of multiple-line households for children who lived in more than one household during the 12 months prior to interview, and to adjust for nonresponse and undercoverage of nontelephone households. The calculation of the RDD sample weights for the Household Survey was done sequentially and consisted of four main steps that included computing a base weight and various adjustments to it. Details about the weighting procedures for the adult and youth data are available in the NISMART-2 HOUSEHOLD SURVEY METHODOLOGY TECHNICAL REPORT which is included in the data collection. Part 3: In order to estimate the national prevalence of facility runaways with known precision, it was necessary to compute facility weights, episode weights, and replicate weights. The facility base weight was the inverse of the unconditional probability of selecting the facility. This was computed as the product of the PSU base weight and the facility base weight. Because there was no nonresponse at the facility level, the facility base weights were also the final facility-level weights. Because data on individual runaways were obtained through the episode-level interviews, the episode weights were equivalent to youth-level weights. These were developed in two steps. First the episode base weight was computed as the inverse of the conditional probability of selecting an episode, taking into account both the probability of selecting the facility that reported the episode and the probability of selecting the episode in question from all episodes reported by the facility. Second, because facilities could not provide details on eight of the 116 episodes they had identified, nonresponse adjustments were computed within facility categories to correct for the absence of these interviews in the episode database. The fact that the study used a multi-stage sampling design (sampling PSUs and then facilities within PSUs) meant that special procedures were required to produce appropriate standard errors for the study estimates. Most standard statistical packages do not produce correct variances because they treat the data as if all the elements in a sample had an equal and independent chance of selection. To allow computation of appropriate standard errors, the replication method was used to develop replicate weights for both the facility and the episode-level data. Thus, the final step in the weighting process was to develop replicate weights. Parts 4-6: Three types of weights were computed for sampled LES cases: agency weights, case weights, and replicate weights. The agency weight is a function of the probability of having selected the agency. Since all law enforcement agencies from the sampled counties were included in the sample, this was the same as the probability of having selected the county. The agency weights were also adjusted for nonresponse and refusals, thus letting the participating agencies represent the additional agencies that would otherwise be unrepresented because of the agencies that did not participate. Case weights took account of the probability of having sampled the case, which was generally the same as the probability of having sampled the agency from which the case originated. The case weights were used to correct for the loss of the two case-level refusals. The final step in the weighting process was the development of replicate weights. The complex sampling design required special procedures in order to compute the precision of the study estimates and conduct statistical tests. The replication approach was used with the LES data. The replication method required the development of replicate weights. While the replication method is not the only way to compute the precision of estimates from complex survey samples, replication methods have been shown to have several advantages even when other methods can be applied. The replicate samples are subsets of the full sample created to mirror the design of the full sample. The technique computes variance by measuring the variability among replicates of the full sample. When a sample includes more than 20 percent of the population, the method of computing replicates must be adjusted. As noted above, it was anticipated that the LES methodology would yield a sample of stereotypical abductions that would reflect a large percentage of the estimated total in the nation. This indeed turned out to be the case. Because of this, the replicates were adjusted with a "finite population factor" in order to avoid overestimating variances Case sampling was used in a few cases to reduce response burden in some large agencies in order to make it feasible for the agency to participate in the study. In these instances, case weights ensured that the sample cases represented all cases in the agency.
Mode of Data Collection: Parts 1-2: computer-assisted telephone interview (CATI), Parts 3-6: telephone interview
Response Rates: Part 1: 35 percent. Part 2: 61 percent. Part 3: The JFS response rate for the institution-level interview was 100 percent. A total of 74 facility-level interviews were completed from the 75 sampled facilities. Three of the sampled facilities were found to be non-operational (hence ineligible), while a fourth sampled facility actually consisted of three separate juvenile residential facilities, all of which were included in the study. Thus, all in-scope facilities participated in the facility-level interviews. The JFS response rate for the episode-level interview was 93 percent. A total of 116 episode-level interviews were targeted. Episode-level interviews were successfully completed for 108 of these targeted episodes, yielding a 93 percent completion rate. Parts 4-6: Phase 1 mail survey -- 91 percent, and Phase 2 followup telephone interview -- 99.3 percent. Overall -- 90.6 percent.
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