This is the same reason why such models are no longer popular in social sciences since the 1970s: responses to policy change are complex and one usually tries (

This is the same reason why such models are no longer popular in social sciences since the 1970s: responses to policy change are complex and one usually tries (with more or less success, which is another topic) to model the micro behavior, so the incentives of actors, rather than find fixed systemic parameters. Cf. Lucas critique Ironically, models without such complexities are often referred to as engineering or physics inspired - from the observation that human behavior is more complex and interdependent than the objects under consideration in physical systems. Natural scientists and engineers delving into social systems frequently fall prey to these issues.