Details on Collective Bargaining per mine (Zondereinde and Booysendal) are found on page 53 of the integrated report (2016). The following calculation was made to get to the 84%:
Zondereinde FY2016 (permanent employees) = 5235 employees with a recognised union.
Booysendal FY2016 (permanent employees) = 24 employees with a recognised union.
5235+24 = 5259
5259/6274 (staff complement of permanent employees)