Table 3.

Crude proportions with silicosis at autopsy of miners, by duration of employment, stratified by population group: 1975–2007 (external causes of death).

Duration of employment (years)	Black			White
	n	Silicosis present	Proportion	n	Silicosis present	Proportion
< 10	11,683	443	0.04	978	19	0.02
10–14	2,815	377	0.13	362	28	0.08
15–19	1,284	286	0.22	320	40	0.13
20–24	400	119	0.30	306	60	0.20
25–29	161	61	0.38	265	74	0.28
> 30	68	18	0.26	501	170	0.34
Total	16,411	1,304	0.08	2,732	391	0.14