The key parameters to technological growth have been identified as societal resources and societal expectations. Both of these are evident functions of technology, and their combined effects can be expected to continue technology's historical exponential growth. This growth pattern would be substantially altered only if we assume that knowledge is bounded or if society makes a conscious decision to stop the flow of resources into the production of new technological options. Although such conscious selection among individual technical fields is to be expected, it is very unlikely to apply to the totality of technology since, as society grows more complex it continuously creates new needs (priority factor), which in turn provide new opportunities for the application of technological options (payoff factor). The analysis also clearly emphasizes the important role which awareness of new technologies plays in forming societal expectations.

These considerations indicate that the technological component of the world simulation model proposed by Meadows et al. (1) and Forrester (2) is best represented by an exponential growth function. The importance of this has been shown by Boyd (3) (Fig. 1), whose "technological optimist" curve has slightly less than exponential growth. Private comnmunication with Boyd indicates that an exponential assumption would reduce the time for equilibrium by several decades. Boyd also indicated that in his modification of the world dynamics model, an exponential technological growth would eventually dominate all other parameters in determining the long-term approach to a steady state. It is evident that the behavior of any world system model is very sensitive to the growth and interaction assumptions for its principal parameters. Thus, model studies should not be easily presumed to represent reality.

The one conclusion that appears to be valid regardless of approach is the evident merit of reducing population growth. The parameter for quality of life shown in Fig. 1, parts 2 and 5, is the product of material levels, overcrowding, food, and pollution. The one factor that a "technological optimist" cannot expect to substantially alter in this model is the effect of overcrowding (Fig. 1, parts 3 and 6). Certainly, the many clear values of reducing population growth and improving the environment do not appear to require the justification of a world system analysis. In like manner, it seems appropriate to encourage the "technological optimist" to provide future options for societal choice, even though there may be present philosophical uncertainties as to their eventual merits. Unlike resources found in nature, technology is a manmade resource whose abundance can be continuously increased, and whose importance in determining the world's future is also increasing.