Year	Number of facilities	label	Mercury emissions per unit of production
2008	288	288	35
2009	277	277	45.5
2010	266	266	24.3
2011	267	267	29.9
2012	271	271	27.5
2013	270	270	27
2014	261	261	25.8
2015	252	252	24.9
2016	254	254	20.1
2017	250	250	20.5