Year	Measure
1990	0.398
1991	0.396
1992	0.397
1993	0.402
1994	0.401
1995	0.405
1996	0.408
1997	0.411
1998	0.413
1999	0.418
2000	0.424
2001	0.433
2002	0.443
2003	0.456
2004	0.467
2005	0.479
2006	0.492
2007	0.504
2008	0.518
2009	0.533
2010	0.543
2011	0.554
2012	0.565
2013	0.57
2014	0.576
2015	0.579