Year	Measure
1990	0.613
1991	0.616
1992	0.616
1993	0.621
1994	0.632
1995	0.642
1996	0.647
1997	0.654
1998	0.664
1999	0.674
2000	0.677
2001	0.686
2002	0.686
2003	0.685
2004	0.692
2005	0.693
2006	0.696
2007	0.7
2008	0.706
2009	0.708
2010	0.721
2011	0.725
2012	0.731
2013	0.735
2014	0.737
2015	0.74