Year	Measure
1990	0.528
1991	0.528
1992	0.534
1993	0.545
1994	0.554
1995	0.564
1996	0.577
1997	0.59
1998	0.59
1999	0.597
2000	0.604
2001	0.608
2002	0.613
2003	0.624
2004	0.629
2005	0.632
2006	0.638
2007	0.641
2008	0.645
2009	0.656
2010	0.662
2011	0.669
2012	0.677
2013	0.682
2014	0.686
2015	0.689