Year	Measure
1990	0.404
1991	0.407
1992	0.399
1993	0.389
1994	0.395
1995	0.408
1996	0.417
1997	0.424
1998	0.424
1999	0.425
2000	0.426
2001	0.428
2002	0.428
2003	0.432
2004	0.435
2005	0.436
2006	0.443
2007	0.441
2008	0.442
2009	0.449
2010	0.457
2011	0.464
2012	0.47
2013	0.475
2014	0.484
2015	0.487