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FUTURE COMPUTING ENVIRONMENTS FOR MICROSIMULATION MODELING 174 income taxes (FEDTAX), state income taxes (STATAX), supplemental security income (SSI), Aid to Families with Dependent Children (AFDC), food stamps (FSTAMP), child nutrition programs (CHINUT), state and local sales taxes (SALETX), state and local property taxes (HOUSE/PROPTX), Medicare and Medicaid (MEDIC), value-added taxes (VAT), and health insurance (HEALTH). The following master routines are used to read or to prepare the TRIM2 database for the simulation process by creating variables required by the major simulation modules: read input files (RDFILE), allocate annual income variables to monthly variables (MONTHS), create random-number variables (RANDOM), create filing unit variables (U8AFDC), adjust asset income (AINC), and impute federal tax deductions (FDIMPU). The following master routines are described below under Output Facilities: export data to an external file format (XPORT), tabulate differences in FSTAMP or AFDC simulations (SIMTAB), produce reports based on income distribution (QUANT), and create one or more output TRIM2 microdata files (WRFTLE). The following TRIM master routines are used to demographically and economically age a prospective TRIM2 microdata file (see Database Adjustment above): projecting the population or population aging (POPAGE), calibrating to a projected unemployment rate (CSWORK), and projecting total income or economic aging (ECONAGE). Most of these simulation and master routines are documented in the TRIM2 Simulation Modules (Webb et al., 1982) and the TRIM2 Reference Manual (Webb et al., 1986). TRIM2 Parameters TRIM2 uses two major types of parameters. Control or supervisor parameters are used to control the overall execution of a TRIM2 job. For example, the NPROC control parameter allows a user to specify the number of households to be processed. Simulation parameters are used to control the execution and output of a simulation module. For example, the FEDTAX simulation module accepts a DIVDEXCL parameter that permits a user to specify the amount of a dividend income exclusion. All TRIM2 parameters are defined and documented in the Central TRIM2 Directory (CTD). The CTD also contains the definitions of all TRIM2 variables and a history of all TRIM2 runs. The CTD is implemented using an indexed sequential access method. Originally, TRIM2 processed the CTD via COBOL subroutines that used the IBM Index Sequential Access Method (ISAM). These routines have now been converted to FORTRAN routines that use the IBM Virtual System Access Method (VSAM). When a data parameter is first entered into the CTD, its basic definition is given. This includes the parameter name; the parameter type (e.g., switch, integer, real); the maximum number of values; and a default simulation name. It is also possible to define an input data parameter that takes one or more parameter names as its values, so the CTD parameter definition also permits