Year	Measure
1990	0.831
1991	0.833
1992	0.835
1993	0.84
1994	0.842
1995	0.846
1996	0.853
1997	0.863
1998	0.872
1999	0.879
2000	0.888
2001	0.89
2002	0.889
2003	0.895
2004	0.899
2005	0.904
2006	0.911
2007	0.914
2008	0.916
2009	0.92
2010	0.932
2011	0.932
2012	0.934
2013	0.936
2014	0.938
2015	0.939