Year	Measure
1990	0.579
1991	0.573
1992	0.561
1993	0.546
1994	0.549
1995	0.554
1996	0.561
1997	0.567
1998	0.575
1999	0.582
2000	0.588
2001	0.599
2002	0.609
2003	0.621
2004	0.637
2005	0.649
2006	0.661
2007	0.673
2008	0.686
2009	0.693
2010	0.701
2011	0.712
2012	0.72
2013	0.729
2014	0.733
2015	0.735