and losers represents one approach to defining the impact of tax and transfer programs. Other forms of analysis are being added to SPSD/M as experience is gained with the system. TRIM2, on the other hand, does not prejudge the principal form of analysis; instead it supplies a general method of data storage to permit selected statistics to be saved for future analysis.
Simulation definition One of the most powerful capabilities embodied in TRIM2 is the concept of its run sequence, which determines which simulation modules are to be run. SPSD/M supports a simple form of run sequence by permitting an analyst to use switch parameters to omit one or more operating characteristics. An additional feature of the TRIM2 run sequence is that it allows an analyst to run the same simulation module multiple times in a single simulation run. This capability is closely tied to the variable naming scheme supported by TRIM2. Neither of these features is supported by the current structure of SPSD/M.
Summary
This comparison of SPSD/M and TRIM2 indicates some of the many similarities and differences between the two systems. Many times, systems with similar objectives are created without the possibility of learning from other designers’ or implemented experiences. We hope this comparison adds to the historical bank of information about problems and techniques for creating socioeconomic microsimulation systems.
ANTICIPATED ADVANCES IN COMPUTING AND INFORMATION TECHNOLOGY
Background
Just as the existence of microsimulation models has depended on the existence of computers, future implementation and use of such models depend on the computing environment that is evolving to support more complex models and new uses. This section addresses the advances expected, in order to assess the opportunities available for the evaluation of microsimulation modeling activities.
Technological progress in the computing industry has provided users with a steady technical dividend on the order of 10–30 percent per year, depending on the specific component and the stage of its evolution. Based on current knowledge of the limitations imposed by physical laws, the size of the market, and computer industry manufacturing techniques, there is no substantial evidence that this rate of technical progress will diminish in the next 5–10 years. For the purposes of this discussion we assume that the current rate of technical progress will continue.
