Year	Measure
1990	0.356
1991	0.352
1992	0.346
1993	0.339
1994	0.333
1995	0.331
1996	0.33
1997	0.333
1998	0.334
1999	0.332
2000	0.331
2001	0.332
2002	0.339
2003	0.347
2004	0.355
2005	0.364
2006	0.37
2007	0.377
2008	0.389
2009	0.395
2010	0.398
2011	0.407
2012	0.412
2013	0.419
2014	0.425
2015	0.435