National Trends in Sulfur_Dioxide Concentrations in 1990 - 2014
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
1990 128.183098591549 142 30 246
1991 121.36690140845 142 30 237
1992 120.232629107981 142 30 232
1993 115.080516431924 142 30 213
1994 115.862089201877 142 28 225
1995 95.1948356807512 142 26 192.6
1996 89.1507042253521 142 23 165
1997 91.9429577464788 142 24 185
1998 91.2661971830985 142 24 187
1999 89.369014084507 142 25 182
2000 80.4443661971831 142 23 163
2001 78.7922535211267 142 21 153
2002 71.4592723004695 142 19 137
2003 72.7760563380281 142 17 152
2004 70.8653755868544 142 19 143
2005 71.8957746478873 142 18 148
2006 68.1110328638497 142 19 138
2007 64.2551643192488 142 16 137
2008 59.8615023474178 142 15 137
2009 49.9026995305164 142 10.6 114
2010 45.8714788732394 142 10 100
2011 38.4616197183098 142 8.6 80.5
2012 35.8097417840375 142 7 76
2013 30.3450704225352 142 6 63
2014 30.2274647887323 142 6.7 65