Year	Measure
1990	0.493
1991	0.493
1992	0.493
1993	0.487
1994	0.489
1995	0.483
1996	0.477
1997	0.468
1998	0.454
1999	0.445
2000	0.443
2001	0.446
2002	0.44
2003	0.439
2004	0.437
2005	0.437
2006	0.44
2007	0.447
2008	0.453
2009	0.464
2010	0.469
2011	0.479
2012	0.484
2013	0.491
2014	0.495
2015	0.497