They're probably misusing the term 'productivity'. In the sense they're speaking it's probably amount of wealth generated by the employee per hour (which isn't the usual definition - quite the opposite).
Arguably if a job pays more then there will be a higher rate of productivity for each hour worked per employee, but again that wouldn't be the normal terminology (since productivity is usually measured by comparing output to labour cost).*
Alternately they could just be talking about productivity among the current (English) unemployed.
* =
http://www.migrationwatchuk.org/Brie...ic_benefit.asp - here they seem to be talking about productivity in a completely independent sense - i.e. we don't need immigrants for the economy to grow.