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FUTURE COMPUTING ENVIRONMENTS FOR MICROSIMULATION MODELING 177 example, the TRIM2 master routine RDFILE can produce a report that includes the number of households, families, and persons read, skipped, processed, or screened out. Several other master routines provide specialized output reports. The SIMTAB operating characteristic is commonly used to compare the results of multiple AFDC or food stamp simulations. The QUANT operating characteristic can provide population distributions of an input file according to a user-selected quantile variable. The OUTFILES control parameter is used to invoke the WRFILE master routine, which is used to create up to four output household microdata files. The following parameters to OUTFILES can be used to determine which variables are written to an output file: NEW, variables created this run; USED, variables used by this run, including NEW variables; ACTIVE, standard list of active file variables, USED variables, and simulated variables with special simulation names; LIST, variables specified by the WRLIST control parameter (can be used to add variables to the above options); and ALL, all variables from the input file plus all NEW variables. TRIM2 offers no built-in facility for user-defined tabulations or statistical analysis unless the user wants to code a custom FORTRAN subroutine. Such a subroutine is then called TALLY and, if linked into the TRIM2 program, can be executed like any other TRIM2 master routine. A TALLY routine can also be used to make modifications to the execution of a TRIM2 model run that cannot be achieved through the use of existing parameters. The XPORT master routine can be used to create output files suitable for processing by SAS, TPL, or SPSS. The observation unit can be the person, the family, the household, or the tax unit (e.g., unmarried adult or married couple), and the output file can be in binary or character. Suitable control cards for the statistical system can also be produced. Auxiliary Models As mentioned above under Database Creation and Database Adjustment, the older TRIM system is still used to carry out functions that have never been converted to function within TRIM2. During conversion of the CPS data file to TRIM2 format, a number of TRIM master routines are used to create variables required by TRIM and TRIM2 and to convert the CPS data file into a TRIM2 household microfile. The aging process used to make a microfile represent future years also uses TRIM master modules. Other Software Facilities Several additional software facilities are included in the TRIM2 system over and above the general ability of running the model. The CTDUSE program is