the world3 model is a system dynamics model for computer simulation of interactions between population, industrial growth, food production and limits in the ecosystems of the earth. it was originally produced and used by a club of rome study that produced the model and the book the limits to growth. the principal creators of the model were donella meadows, dennis meadows, and jÃ¸rgen randers. the model was documented in the book dynamics of growth in a finite world. it added new features to jay w. forrester's world2 model. since world3 was originally created it has had minor tweaks to get to the world3/91 model used in the book beyond the limits, later improved to get the world3/2000 model distributed by the institute for policy and social science research and finally the world3/2004 model used in the book limits to growth: the 30 year update. world3 is one of several global models that have been generated throughout the world (mesarovic/pestel model, bariloche model, moira model, saru model, fugi model) and is probably the model that generated the spark for all later models. == model == the model consisted of several interacting parts. each of these dealt with a different system of the model. the main systems were *the food system, dealing with agriculture and food production, *the industrial system, *the population system, *the non-renewable resources system, *the pollution system. === agricultural system === the simplest useful view of this system is that land and fertilizer are used for farming, and more of either will produce more food. in the context of the model, since land is finite, and industrial output required to produce fertilizer and other agricultural inputs can not keep up with demand, there necessarily will be a food collapse at some point in the future. === nonrenewable resources system ===  the nonrenewable resource system starts with the assumption that the total amount of resources available is finite (about 110 times the consumption at 1990s rates for the world3/91 model). these resources can be extracted and then used for various purposes in other systems in the model. an important assumption that was made is that as the nonrenewable resources are extracted, the remaining resources are increasingly difficult to extract, thus diverting more and more industrial output to resource extraction. === reference run predictions === the dynamics of growth in a finite world book provides multiple different scenarios. the "reference run" is the one that the authors state "represent the most likely behavior mode of the system if the process of industrialization in the future proceeds in a way very similar to its progress in the past, and if technologies and value changes that have already been institutionalized continue to evolve."dynamics of growth in a finite world, pg 502 i
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