Year	Measure
1990	0.556
1991	0.56
1992	0.566
1993	0.569
1994	0.574
1995	0.577
1996	0.581
1997	0.586
1998	0.589
1999	0.588
2000	0.589
2001	0.596
2002	0.599
2003	0.61
2004	0.624
2005	0.636
2006	0.644
2007	0.651
2008	0.648
2009	0.65
2010	0.646
2011	0.645
2012	0.635
2013	0.575
2014	0.553
2015	0.536