  We introduced a decision-making model based on value functions that included
individualistic utility function and socio-constructivistic norm function and
proposed a norm-fostering process that recursively updates norm function
through mutual recognition between the self and others. As an example, we
looked at the resource-sharing problem typical of economic activities and
assumed the distribution of individual actions to define the (1) norm function
fostered through mutual comparison of value/action ratio based on the equity
theory (progressive tax-like), (2) norm function proportional to resource
utilization (proportional tax-like) and (3) fixed norm function independent of
resource utilization (fixed tax-like). By carrying out numerical simulation, we
showed that the progressive tax-like norm function (i) does not increase
disparity for the distribution of the actions, unlike the other norm functions,
and (ii) has high resource productivity and low Gini coefficient. Therefore the
progressive tax-like norm function has the highest sustainability and fairness.
