Year	Measure
1990	0.507
1991	0.509
1992	0.514
1993	0.522
1994	0.525
1995	0.53
1996	0.536
1997	0.543
1998	0.548
1999	0.551
2000	0.557
2001	0.561
2002	0.566
2003	0.571
2004	0.577
2005	0.583
2006	0.59
2007	0.597
2008	0.603
2009	0.606
2010	0.611
2011	0.614
2012	0.614
2013	0.618
2014	0.623
2015	0.625