D. growth of neither public nor private sector unions
Explanation:
In recent years both Public and private unions have lost popularity among the workers as they have been slowly losing their importance in the modern capitalistic societies.
Union memberships were important for the security of the rights of the workers and these unions were often quite influential too. This has not remained the case unfortunately.
With sanctions in place, unions do not have an effective job to do and their popularity has dwindled.
