National Trends in Sulfur_Dioxide Concentrations in 1980 - 2012
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
1980 147.3 57 40 271
1981 141.027192982456 57 40 251
1982 129.169590643274 57 25 250
1983 138.449707602339 57 34 300
1984 129.950877192982 57 30 263
1985 128.168421052631 57 30 249
1986 129.093859649122 57 30 248
1987 125.666666666666 57 25 280
1988 129.067251461988 57 30 267
1989 123.951461988304 57 30 261
1990 109.472514619883 57 22 226
1991 103.961403508771 57 26 218
1992 101.140935672514 57 20 210
1993 93.4900584795321 57 30 200
1994 95.4093567251462 57 26 181
1995 85.5631578947368 57 25 216
1996 81.8157894736842 57 24 160
1997 82.4070175438596 57 23 181
1998 82.2087719298245 57 26 185
1999 84.8070175438596 57 25 195.5
2000 77.6210526315789 57 26 163
2001 78.5017543859649 57 26 203
2002 68.8245614035087 57 17 145
2003 72.4666666666666 57 17 176
2004 68.7315789473684 57 18 172
2005 67.2479532163742 57 16 143
2006 62.2888888888889 57 20 138
2007 56.9877192982456 57 17 137.3
2008 51.2099415204678 57 16 111
2009 44.6619883040935 57 9.5 96
2010 40.2836257309941 57 9.66666666666666 84.3
2011 33.8040935672514 57 8 68
2012 32.7140350877193 57 7.3 65.4