Other metrics assess the impact of alignments externally, e.g., different alignments are tested by comparing the corresponding MT outputs using automated evaluation metrics (e.g., BLEU (Papineni et al., 2002) or METEOR (Banerjee and Lavie, 2005)).
these studies showed that AER and BLEU do not correlate well (Callison-Burch et al., 2004;Goutte et al., 2004;Ittycheriah and Roukos, 2005).