National Trends in Sulfur_Dioxide Concentrations in 1980 - 2008

Year	Mean	Number of Trend Sites	10th Percentile	90th Percentile
1980	0.01190283687943	141	0.0039	0.0218
1981	0.01147730496453	141	0.0038	0.0195
1982	0.01035283687943	141	0.0036	0.0176
1983	0.01001903073286	141	0.0035	0.0167
1984	0.01019952718676	141	0.0029	0.0167
1985	0.00966903073286	141	0.0027	0.017
1986	0.00925059101654	141	0.0025	0.0152
1987	0.00908026004728	141	0.0027	0.0151
1988	0.00943853427895	141	0.0028	0.0153
1989	0.00892529550827	141	0.0027	0.0144
1990	0.00854822695035	141	0.0026	0.0145
1991	0.00827517730496	141	0.0024	0.0136
1992	0.00772234042553	141	0.0025	0.0126
1993	0.00768014184397	141	0.0028	0.0125
1994	0.00747234042553	141	0.0023	0.0125
1995	0.00598262411347	141	0.002	0.0109
1996	0.00597021276595	141	0.0021	0.0104
1997	0.00590638297872	141	0.0021	0.0095
1998	0.00564468085106	141	0.0024	0.0096
1999	0.00539621749408	141	0.0023	0.0091
2000	0.00520591016548	141	0.0022	0.0086
2001	0.00491560283687	141	0.0019	0.0082
2002	0.00456241134751	141	0.0018	0.0074
2003	0.00449574468085	141	0.0019	0.008
2004	0.00436241134751	141	0.0018	0.0074
2005	0.00440165484633	141	0.0018	0.0071
2006	0.00391607565011	141	0.0016	0.0067
2007	0.00378936170212	141	0.0015	0.0063
2008	0.00339730496453	141	0.0014	0.0058