National Trends in Sulfur_Dioxide Concentrations in 1990 - 2012
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
1990 123.717791411042 163 30 246
1991 117.614110429447 163 30 237
1992 117.429652351738 163 30 232
1993 111.389161554192 163 30 213
1994 112.742842535787 163 28 223
1995 91.3803680981595 163 25 183
1996 86.4472392638036 163 23 164
1997 88.2212678936605 163 24 172
1998 87.8995910020449 163 25 185
1999 86.3867075664621 163 25 178
2000 78.4869120654396 163 24 163
2001 76.321472392638 163 21 151
2002 69.1225971370143 163 19 137
2003 70.5683026584867 163 17 146
2004 67.8940695296523 163 19 143
2005 68.2134969325153 163 17 140
2006 64.7292433537832 163 16 138
2007 60.3910020449897 163 16 135
2008 56.2376278118609 163 15 131
2009 47.2096114519427 163 10 109
2010 43.0620654396728 163 10 91
2011 36.5471370143149 163 8.6 79
2012 34.6668711656441 163 7 76