Year	Measure
1990	0.309
1991	0.31
1992	0.303
1993	0.311
1994	0.314
1995	0.32
1996	0.336
1997	0.351
1998	0.366
1999	0.382
2000	0.396
2001	0.404
2002	0.418
2003	0.427
2004	0.429
2005	0.434
2006	0.442
2007	0.453
2008	0.464
2009	0.473
2010	0.477
2011	0.477
2012	0.478
2013	0.483
2014	0.488
2015	0.493