Fig. 3. Examples of the migration function (y-axis scale on left), f(x,am,bm) = 0.5 + arctan(am(x−bm))/π and g(x,ag,bg) = arctan(ag(x−bg))/π (y-axis scale on right) for different values of am and bm. The parameters am and ag control the steepness of the function, i.e., how well agents can measure and assess differences in consumption possibilities or how rapidly population growth increases with higher food intake, respectively. The parameters bm and bg shift the functions horizontally. Shifting the function to the right could represent increasing transaction costs to migrate or a higher nutritional threshold before population growth becomes positive.
Fig. 3