National Trends in Carbon_Monoxide Concentrations in 1980 - 2012
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
1980 8.9314606741573 89 4.4 13
1981 8.83876404494382 89 3.9 13
1982 8.37153558052434 89 4.6 12.9
1983 8.52846441947565 89 4 13.2
1984 7.97584269662921 89 4.4 11.9
1985 7.39831460674157 89 4 12.2
1986 7.67078651685393 89 3.9 11.7
1987 6.90561797752808 89 3.9 9.6
1988 6.72584269662921 89 4.1 10.3
1989 6.82247191011236 89 3.7 10.4
1990 6.35580524344569 89 3.5 10
1991 6.07677902621722 89 3.3 9.4
1992 5.50786516853932 89 3.3 8
1993 5.23370786516854 89 3.1 7.6
1994 5.36741573033707 89 3.2 8
1995 4.82022471910112 89 2.7 7.4
1996 4.46853932584269 89 2.7 6.9
1997 4.12808988764044 89 2.4 6.4
1998 3.99550561797752 89 2.3 5.9
1999 4.0067415730337 89 2.4 6.2
2000 3.48539325842696 89 2 5.4
2001 3.30224719101123 89 1.9 4.8
2002 2.86404494382022 89 1.8 4.4
2003 2.68876404494382 89 1.7 3.8
2004 2.51123595505618 89 1.5 3.7
2005 2.29157303370786 89 1.4 3.3
2006 2.2191011235955 89 1.3 3.3
2007 1.9438202247191 89 1.2 2.9
2008 1.75730337078651 89 1.1 2.6
2009 1.67977528089887 89 1 2.5
2010 1.56404494382022 89 0.9 2.3
2011 1.63483146067415 89 0.9 2.4
2012 1.51235955056179 89 0.9 2.1