I’m big on models that provide compact, interpretable summaries of complicated underlying mechanisms. Such models have great generality–they apply to any system in which the effects of the underlying mechanisms can be summarized in the way the model summarizes them. The Price equation is one example (there are of course many, many others).
For instance, here’s a new paper on gang warfare in Los Angeles based on the spatial Lotka-Volterra competition equations (!) Non-technical summary here (which I can’t vouch for as I haven’t read the paper yet; will try to update if/when I get a chance to do so). The parameters of the Lotka-Volterra equations can be interpreted so as to summarize the underlying mechanisms that govern gang territory size and determine the spatial distribution of gang warfare.
HT to my Calgary colleague Kyla Flanagan
Dynamic Ecology 