Table 1.

Explanation of variables from the database used for this study

Variable on database	Comment or further description	Derived Variables
South African ID number	Available only to statistician with access to South African Rapid Mortality Surveillance and not to researchers.	Vital status and date of death if deceased, 2011–2013.
Unique key	TEBA randomly assigned number available to the researchers.
Racial ascription (race)a	Four category classification formalised under apartheid, and in continuing usage for most official purposes – “Asian, black, coloured, white”.
Contract days	Sum of all days worked across all contracts.	Cumulative employment across all contracts.
Commodity mined	Gold, platinum group metals, coal, “other” (antimony, asbestos, chrome, copper, diamond, granite, iron, lead, lime, tin, vanadium).b	Commodity sector exclusively worked. Mixed service across sectors.
Occupational category	Underground, surface.	Occupational category exclusively worked. Mixed employment across occupational categories.
Nature of employment contract	Miners employed by the mining company distinguished from those employed by a third party contractor or via labour brokers.

^aBlack miners, the majority of whom are or were migrants recruited from rural areas of South Africa and neighbouring countries, make up most of the mining workforce, and whites a significant minority. These categories have strong economic and social correlates, including in this context, occupational grade, earnings, area of origin, and lifetime health experience

^bIncludes unassigned employees recorded as “Medical”, “Security”, “Training” and “Sundry”