Year	Measure
1990	0.478
1991	0.484
1992	0.49
1993	0.495
1994	0.5
1995	0.507
1996	0.515
1997	0.523
1998	0.531
1999	0.539
2000	0.546
2001	0.553
2002	0.56
2003	0.564
2004	0.567
2005	0.57
2006	0.578
2007	0.589
2008	0.596
2009	0.602
2010	0.609
2011	0.616
2012	0.611
2013	0.614
2014	0.637
2015	0.64