Year	Measure
1990	0.634
1991	0.628
1992	0.595
1993	0.593
1994	0.597
1995	0.603
1996	0.609
1997	0.618
1998	0.632
1999	0.639
2000	0.644
2001	0.645
2002	0.657
2003	0.668
2004	0.679
2005	0.692
2006	0.707
2007	0.721
2008	0.725
2009	0.72
2010	0.729
2011	0.732
2012	0.736
2013	0.739
2014	0.741
2015	0.743