Training set statistics comparisons against previous aspect-based summarization datasets. For multi-domain datasets, the sum of all the examples are reported. #Asp./Ex. represents the average number of aspects that a model has to summarize on each example. (*Review saliency is treated as aspects. #Asp. represents the number of aspects per domain if the number of domains is more than one. Compared datasets are the work of Angelidis and Lapata (2018); Yang et al. (2018); Wang and Ling (2016); Frermann and Klementiev (2019), respectively.