Our language difficulty estimates were largely stable across datasets and language model architectures, but they were not significantly predicted by linguistic factors.
we compute HPE-mean from dependency parses of the Europarl data, generated using UDPipe 1.2.0 (Straka et al., 2016) and freely-available tokenization, tagging, parsing models trained on the Universal Dependencies 2.0 treebanks (Straka and Straková, 2017).