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Local-Area Crime Survey, [United States], 2015, 2016
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The Bureau of Justice Statistics (BJS) entered into a cooperative agreement with Westat to develop and evaluate a lower-cost, subnational companion survey of victimization as one piece of the subnational estimates program. The Local-Area Crime Survey (LACS) was fielded in 2015 and 2016 and is intended for use by states, municipalities, or other jurisdictions and entities to assess levels and trends in public safety. The LACS is modeled in part after the National Crime Victimization Survey (NCVS), conducted for BJS by the U.S. Census Bureau. One of the two major statistical programs on crime produced by the U.S. Department of Justice, the NCVS is the nation's primary source of information about criminal victimization, whether reported or not reported to police. The core NCVS methodology includes a mix of in-person and telephone interviews with household members age 12 and older selected from an area probability sample to produce reliable national-level estimates. As another part of the subnational estimates program, BJS worked with the Census Bureau to enhance and reallocate the NCVS sample to support subnational estimates for the 22 most populous states and potentially substate areas within those states. For the most part, this direct estimation component of the program will not support estimates at the local level. See the NCVS Subnational Estimates webpage on the BJS website for more information.
The goals of this research were to (1) develop and test a relatively inexpensive survey design (2) that could be administered by local jurisdictions or their vendors (3) to produce cross-jurisdiction estimates and estimates of change over time within jurisdictions that may be compared with similar estimates using NCVS data. In addition to questions about victimization experiences, the LACS included questions about perceptions of community safety and police efficacy. The rationale for including these items was that they were relevant to all households, not just victims. The hope was that these items would increase survey response rates as non-victims would have important questions to answer. The LACS served as a platform for assessing the value of these questions for the planned NCVS instrument redesign. For more information, see the NCVS Instrument Redesign webpage on the BJS website.
Detailed Methodology
The sample universe for the field test included residential addresses in the 40 largest CBSAs (as of 2015) in the United States. All adults in residential households were eligible for the study; those living in institutional settings, including group quarters, were excluded from the study. The sampling frame for both years used an address-based sample (ABS), with a U.S. Postal Service (USPS) list of addresses. In year 1 of the study, three of the CBSAs were oversampled to generate sub-CBSA estimates. These substrata were defined based on police jurisdiction boundaries in Chicago, Los Angeles, and Philadelphia. In year 2 of the study, oversamples were included for Chicago and Philadelphia, and the year 2 sample included a 25% overlap with the year 1 sampled addresses (the remaining addresses were selected from the most recent, available address frame).
The year 1 target number of completed surveys for each of the 37 non-oversampled CBSAs (all CBSAs except Philadelphia, Los Angeles, and Chicago) was 2,100 completed surveys. The target sample sizes for the three oversampled CBSAs were 7,500 completed surveys for Los Angeles, 7,500 for Chicago, and 9,363 for Philadelphia. Based on a general assumption of a 50% response rate and 11% vacancy rate, the starting sample was 229,475.
The year 2 sample design was similar, although there were 38 non-oversampled CBSAs (Los Angeles was not oversampled in year 2). The year 2 target sample sizes for the non-oversampled and two oversampled CBSAs were the same as for year 1. The study design included randomly assigning a portion of the sampled addresses to be included in both years. The 25 percent overlap sample was selected from the year 1 sample while the new portion of the year 2 sample was selected from the most recent USPS address lists using the same procedures as used in year 1.
Sampled addresses were randomly assigned to equal-sized treatment groups by sorting the sample within CBSA (or CBSA stratum) and instrument (person-level survey or incident-level survey) by state, county, Census tract and Census block group, then numbering the addresses from 1 to 'x' repeatedly until all addresses were assigned a number (where 'x' equals the number of experimental treatments in that year of the field test). The research team developed two instrumentation approaches for collecting victimization data. One instrument version was based on collecting information about individual incidents (coined the "incident-level survey" or ILS). In this version, the household proxy respondent was asked to enumerate victimization incidents, then link those incidents to the relevant adult victim described in a roster. A second version was based on collecting victimization prevalence for each adult household member (the "person-level survey" or PLS).
The population of inference for the LACS was all residential adults, and a single household member acted as a proxy for the remaining adult household members. In year 2, this was done separately for the new and overlap portions of the sample. The starting sample in year 1 was 229,475, split between the PLS and the ILS instrument. In year 2, the starting sample of 217,250 was slightly smaller because one of the CBSAs oversampled in year 1 (Los Angeles) was not oversampled in year 2.
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