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Suggested Citation:"Database Adjustment." National Research Council. 1991. Improving Information for Social Policy Decisions -- The Uses of Microsimulation Modeling: Volume II, Technical Papers. Washington, DC: The National Academies Press. doi: 10.17226/1853.
Page 172

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FUTURE COMPUTING ENVIRONMENTS FOR MICROSIMULATION MODELING 172 to one of four compressed formats: full word (4 bytes), 1 byte (8 bits), 4 bits, or 1 bit. Table 5 indicates the approximate size of the 1986 TRIM2 master file as it is stored using the above types of compression. Tables 4 and 5 indicate that the compression techniques used by TRIM2 reduce the size of the raw data by over 50 percent. TABLE 5 1986 TRIM2 Compressed Master File Size Data Records No. of Fields No. of Records Size of Record (bytes) Total Size (MB) Family 79 63,741 121 7.71 Person 75 155,372 60 9.32 Adult 287 119,704 698 83.55 1986 master 100.58 A TRIM2 active file contains a predefined set of the most commonly used TRIM2 variables. Many simulation projects can use the default active file by itself without referencing the master file. If required variables are missing from the initial active file, a single TRIM2 job can be executed to add the missing variables to the active file, which can then be used for simulation purposes. For efficiency reasons, data are not compressed on an active file, since the assumption is that most if not all variables will be required during a simulation run. For example, Table 6 describes the default active file for the 1986 TRIM2 database. It also indicates that many simulation runs can decrease the amount of data that must be read by a factor of up to five by using an active file instead of the associated master file. While a TRIM2 data file includes a description of each variable on the file, it also contains, as historical information, the control cards used to create the file and the historical data from each input file used during the creating job. Therefore, since the historical data for the input data files contain the historical data of their antecedents, the complete history of how a file was created is stored with the file. Both the variable descriptions and historical information can be printed using the MICRODOC software utility. Database Adjustment TRIM2 can simulate tax and transfer programs in future years by aging the base-year CPS data. An aging scenario can be based on a future population distribution or an economic outlook based on an unemployment rate or labor force participation rate. Unfortunately, the master routines required to carry out this type of database adjustment are part of the software used to convert the CPS data file to TRIM2 format and have never been converted to run within

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Improving Information for Social Policy Decisions -- The Uses of Microsimulation Modeling: Volume II, Technical Papers Get This Book
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This volume, second in the series, provides essential background material for policy analysts, researchers, statisticians, and others interested in the application of microsimulation techniques to develop estimates of the costs and population impacts of proposed changes in government policies ranging from welfare to retirement income to health care to taxes.

The material spans data inputs to models, design and computer implementation of models, validation of model outputs, and model documentation.

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