year	pollutant_name	index
2000	PM2.5	100.0
2001	PM2.5	98.8
2002	PM2.5	96.7
2003	PM2.5	97.9
2004	PM2.5	99.2
2005	PM2.5	97.1
2006	PM2.5	93.8
2007	PM2.5	91.3
2008	PM2.5	86.6
2009	PM2.5	80.8
2010	PM2.5	75.8
2011	PM2.5	72.1
2012	PM2.5	67.4
2013	PM2.5	61.8
2014	PM2.5	59.7
2015	PM2.5	56.4
2016	PM2.5	57.8