Year	Measure
1990	0.596
1991	0.601
1992	0.61
1993	0.617
1994	0.622
1995	0.628
1996	0.634
1997	0.64
1998	0.645
1999	0.651
2000	0.656
2001	0.66
2002	0.665
2003	0.666
2004	0.668
2005	0.677
2006	0.685
2007	0.692
2008	0.695
2009	0.697
2010	0.703
2011	0.706
2012	0.709
2013	0.712
2014	0.718
2015	0.722