National Trends in Carbon_Monoxide Concentrations in 1980 - 2010
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
1980 8.82884615384615 104 4.4 14.1
1981 8.74663461538461 104 3.9 13.6
1982 8.27083333333333 104 3.9 13.2
1983 8.37628205128205 104 4 13.2
1984 7.89086538461538 104 4.4 11.9
1985 7.43798076923076 104 3.9 12.2
1986 7.63942307692307 104 3.9 11.4
1987 6.87307692307691 104 3.8 9.7
1988 6.78509615384615 104 3.9 10.3
1989 6.81057692307692 104 3.7 10.3
1990 6.23621794871795 104 3.4 9.7
1991 6.00032051282051 104 3.3 9.4
1992 5.5125 104 3.1 8
1993 5.22980769230769 104 2.9 7.6
1994 5.36826923076923 104 3.1 8
1995 4.81346153846154 104 2.7 7.4
1996 4.50865384615384 104 2.7 6.9
1997 4.22211538461538 104 2.4 6.4
1998 3.96346153846153 104 2.1 5.9
1999 4.01153846153846 104 2.2 6.2
2000 3.51730769230769 104 1.9 5.4
2001 3.30673076923076 104 1.9 4.8
2002 2.8826923076923 104 1.8 4.4
2003 2.72403846153846 104 1.7 3.9
2004 2.53461538461538 104 1.5 3.7
2005 2.30817307692307 104 1.4 3.3
2006 2.21153846153846 104 1.3 3.3
2007 1.95192307692307 104 1.2 3
2008 1.76538461538461 104 1.1 2.6
2009 1.67884615384615 104 1 2.5
2010 1.57884615384615 104 0.9 2.3