Year	Measure
1990	0.541
1991	0.537
1992	0.552
1993	0.566
1994	0.576
1995	0.582
1996	0.592
1997	0.597
1998	0.599
1999	0.602
2000	0.606
2001	0.609
2002	0.611
2003	0.613
2004	0.619
2005	0.622
2006	0.62
2007	0.618
2008	0.618
2009	0.618
2010	0.624
2011	0.63
2012	0.633
2013	0.636
2014	0.638
2015	0.638