  The quantum paradigm presents a phenomenon known as degeneracy that should
improve the performance of quantum error correcting codes. However, the effects
of this mechanism are sometimes ignored when evaluating the performance of
sparse quantum codes and the logical error rate is not always correctly
reported. In this paper, we discuss previously existing methods to compute the
logical error rate and we present an efficient coset-based method inspired by
classical coding strategies to estimate degenerate errors. Additionally, we
show that the proposed method presents a computational advantage for the family
of Calderbank-Shor-Steane codes. We use this method to prove that degenerate
errors are frequent in a specific family of sparse quantum codes, which
stresses the importance of accurately reporting their performance. Our results
also reveal that the modified decoding strategies proposed in the literature
are an important tool to improve the performance of sparse quantum codes.
