Incorporating Discrete Translation Lexicons into Neural Machine Translation
(b) KFTT
['Lexicon', 'BLEU bias', 'BLEU linear', 'NIST bias', 'NIST linear']
In general the bias method improves accuracy for the auto and hyb lexicon, but is less effective for the man lexicon. This is likely due to the fact that the manual lexicon, despite having broad coverage, did not sufficiently cover target-domain words (coverage of unique words in the source vocabulary was 35.3% and 9.7% for BTEC and KFTT respectively).