Year	Measure
1990	0.797
1991	0.809
1992	0.812
1993	0.812
1994	0.818
1995	0.82
1996	0.825
1997	0.833
1998	0.843
1999	0.847
2000	0.854
2001	0.859
2002	0.866
2003	0.873
2004	0.879
2005	0.884
2006	0.887
2007	0.892
2008	0.894
2009	0.894
2010	0.894
2011	0.901
2012	0.907
2013	0.915
2014	0.919
2015	0.921