Year	Measure
1990	0.535
1991	0.543
1992	0.549
1993	0.556
1994	0.564
1995	0.571
1996	0.577
1997	0.579
1998	0.591
1999	0.6
2000	0.607
2001	0.61
2002	0.617
2003	0.62
2004	0.622
2005	0.625
2006	0.626
2007	0.632
2008	0.636
2009	0.643
2010	0.649
2011	0.655
2012	0.661
2013	0.666
2014	0.671
2015	0.674