A multi-agent-based approach to tax morale
  We embed the behaviour of tax evasion into the standard two-dimensional Ising model. In the presence of an external magnetic field, the Ising model is able to generate the empirically observed effect of tax morale, i.e. the phenomenon that in some countries tax evasion is either rather high or low. The external magnetic field captures the agents' trust in governmental institutions. We also find that tax authorities may curb tax evasion via appropriate enforcement mechanisms. Our results are robust for the Barab\'asi-Albert and Voronoi-Delaunay networks. 
G. Zaklan, F. W. S. Lima, F. Westerhoff