National Trends in Carbon_Monoxide Concentrations in 1990 - 2012
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
1990 6.1 148 3.3 9.5
1991 6.00202702702702 148 3.3 9.4
1992 5.45945945945946 148 3 8.1
1993 5.14121621621621 148 3 7.5
1994 5.35304054054054 148 2.8 8
1995 4.72702702702702 148 2.5 7.4
1996 4.42128378378378 148 2.5 6.9
1997 4.18175675675675 148 2.2 6.4
1998 4.07229729729729 148 2.3 6.3
1999 3.91689189189189 148 2.2 6.2
2000 3.52837837837837 148 1.9 5.6
2001 3.275 148 1.8 4.8
2002 2.97702702702702 148 1.8 4.4
2003 2.77229729729729 148 1.6 4.1
2004 2.58648648648648 148 1.4 3.8
2005 2.29831081081081 148 1.4 3.4
2006 2.23581081081081 148 1.3 3.3
2007 1.9331081081081 148 1.2 3
2008 1.79391891891891 148 1.1 2.7
2009 1.7277027027027 148 1 2.5
2010 1.56891891891891 148 0.9 2.3
2011 1.59527027027027 148 0.9 2.3
2012 1.50675675675675 148 0.9 2.1