Year	Measure
1990	0.651
1991	0.656
1992	0.658
1993	0.667
1994	0.669
1995	0.671
1996	0.675
1997	0.677
1998	0.678
1999	0.682
2000	0.68
2001	0.69
2002	0.694
2003	0.689
2004	0.706
2005	0.709
2006	0.714
2007	0.718
2008	0.721
2009	0.721
2010	0.722
2011	0.725
2012	0.727
2013	0.727
2014	0.729
2015	0.73