If a sparse matrix has only 1% non-zero entries, I find it weird to speak of "1% sparsity". In particular, "increasing sparsity" goes along with a smaller percentage of non-zero entries, so this is determined to cause confusion. However, I have never read about a matrix with "99% sparsity", expressing that the matrix has 1% non-zero entries. The number of non-zero entries seems to be what's used to characterize a sparse matrix.
So which word to use? The dictionary proposes "density", but that may sound odd. A sparse matrix with 1% density? Sure, if there's nothing better. Or is there?
Non-subjective variant of my question: What are terms used by other authors for the fraction of non-zero entries in a sparse matrix?