Monolingual post-editors Experts in the domain, but not bilingual Bilingual post-editors Professional translators with domain expertise, they are trained to understand issues with MT and not only correct the error in the sentence, but work to create rules for the MT engine to follow. A fully qualified professional translator has to have two sets of skills when translating a text. On the one hand the language skills to generally understand the source language and to write well in the target language, and on the other hand the domain knowledge to understand the content of a possibly very specialized technical document. Both skill sets may be hard to find, especially in combination. In fact, it is common practice in the translation industry to differentiate translators according to their qualifications.
While automated metrics such as BLEU and human metrics such as Edit Distance are useful indicators of quality, by themselves they do not provide enough information. Productivity is the metric that matters most to LSPs as this relates directly to profit margin. Measuring productivity provides LSPs and post-editors with a simple means to determine a fair rate for MT post-editing. A fair rate can be established based upon the productivity gain realized via an MT + human approach and the reduced effort required to deliver the same quality output. If post-editing MT is 3 times faster than a human only translation only approach, then there is justification for reducing rates by 33% of the regular rate, but generally since this is just a small sample it would be wiser to adjust this upwards to a level that may accommodate more variance in the MT output. From the translators perspective, they are being paid less per word, but are being paid more per hour overall.