The reason seems to be that the generation of a ranking by negativity seems a somehow harder task than the generation of a ranking by positivity; this is also shown by the results obtained with the uniform-valued vector e1, in which the application of PageRank improves with respect to e1 for positivity but deteriorates for negativity.
against the baseline constituted by the results obtained with the uniformvalued vector e1 for negativity, our rankings show a relevant improvement, ranging from −8.56% (e2) to −48.27% (e4).