National Trends in Carbon_Monoxide Concentrations in 2000 - 2012
Year Mean Number of Trend Sites 10th Percentile 90th Percentile
2000 3.52755555555555 225 1.6 5.6
2001 3.31866666666666 225 1.6 4.9
2002 2.97422222222222 225 1.5 4.7
2003 2.76622222222222 225 1.4 4.3
2004 2.56355555555555 225 1.3 3.9
2005 2.32777777777777 225 1.2 3.6
2006 2.23088888888888 225 1.1 3.4
2007 1.95799999999999 225 1.1 3
2008 1.83244444444444 225 1 2.8
2009 1.75244444444444 225 0.9 2.6
2010 1.61377777777777 225 0.8 2.4
2011 1.60266666666666 225 0.9 2.4
2012 1.51288888888888 225 0.8 2.2