  In this brief report, we prove that robustness of coherence (ROC), in
contrast to many popular quantitative measures of quantum coherence derived
from the resource theoretic framework of coherence, may be sub-additive for a
specific class of multipartite quantum states. We investigate how the
sub-additivity is affected by admixture with other classes of states for which
ROC is super-additive. We show that pairs of quantum states may have different
orderings with respect to relative entropy of coherence, $l_{1}$-norm of
coherence and ROC and numerically study the difference in ordering for
coherence measures chosen pairwise.
