comma btw subject and verb: countries whose wage levels..., are

This unfair competition is induced by the fact that countries whose wage levels are extremely low, are catching up with developed countries concerning their productivity;

My question is: do I need to put the comma after low? I don't know if it's necessary.
  • Matching Mole

    Senior Member
    England, English
    "Countries whose wage levels are extremely low" is the subject of the verb phrase "are catching up": the relative phrase is essential (or defining) to the subject, so putting a comma there is like putting a comma between a subject and a verb, which we should not do.

    It's a bit like:
    "People whose habits are annoying, are not very popular"; I think it's easy to see that this is incorrect.