National Trends in Carbon_Monoxide Concentrations in 1990 - 2010
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
1990 5.98058823529411 170 3.2 9.25
1991 5.88999999999999 170 3.1 9.4
1992 5.40117647058823 170 2.85 8.05
1993 5.11235294117647 170 2.8 7.55
1994 5.31558823529411 170 2.8 8
1995 4.71235294117647 170 2.45 7.4
1996 4.41088235294117 170 2.4 6.8
1997 4.19441176470588 170 2.2 6.4
1998 4.00647058823529 170 2 6.3
1999 3.89588235294117 170 1.95 6.2
2000 3.51764705882352 170 1.8 5.5
2001 3.2535294117647 170 1.75 4.8
2002 2.95764705882352 170 1.7 4.4
2003 2.77411764705882 170 1.55 4.25
2004 2.57411764705882 170 1.4 3.85
2005 2.29382352941176 170 1.4 3.4
2006 2.21470588235294 170 1.3 3.3
2007 1.9335294117647 170 1.2 3
2008 1.78823529411764 170 1.05 2.7
2009 1.71647058823529 170 1 2.55
2010 1.57705882352941 170 0.9 2.3