Table 2

Variance components and contrast using different grouping strategies

	Number of groups	_BGS_y²	_WGS_y²	_WWS_y²	_TOTALS_y²	Contrast
_BGS_y², between-group variance; _WGS_y², within-group variance; _WWS_y², within-worker variance; _TOTALS_y², total variance.
Contrast in exposure between groups: _BGS_y²/_BGS_y² + _WGS_y².
*A total of 324 groups was possible. For 78 groups no measurements were available, leaving 246 groups for the analysis.
Tasks	6	0.089	0.208	0.264	0.558	0.300
Automation	4	0.009	0.263	0.275	0.547	0.033
Factory size	2	0.053	0.259	0.275	0.586	0.170
Use of compressed air	2	0.038	0.348	0.275	0.562	0.098
Factory	54	0.062	0.210	0.275	0.546	0.228
Task + factory size	12	0.139	0.136	0.263	0.538	0.505
Task + factory	246*	0.142	0.134	0.2635	0.539	0.514
Task + factory, quintiles	5	0.204	0.115	0.263	0.582	0.639