  We have studied few social inequality measures associated with the
sub-critical dynamical features (measured in terms of the avalanche size
distributions) of four self-organized critical models while the corresponding
systems approach their respective stationary critical states. It has been
observed that these inequality measures (specifically the Gini and Kolkata
indices) exhibit nearly universal values though the models studied here are
widely different, namely the Bak-Tang-Wiesenfeld sandpile, the Manna sandpile
and the quenched Edwards-Wilkinson interface, and the fiber bundle interface.
These observations suggest that the self-organized critical systems have broad
similarity in terms of these inequality measures. A comparison with similar
earlier observations in the data of socio-economic systems with unrestricted
competitions suggest the emergent inequality as a result of the possible
proximity to the self-organized critical states.
