Year	Measure
1990	0.32
1991	0.314
1992	0.302
1993	0.302
1994	0.304
1995	0.307
1996	0.304
1997	0.307
1998	0.309
1999	0.312
2000	0.314
2001	0.315
2002	0.316
2003	0.315
2004	0.319
2005	0.323
2006	0.33
2007	0.338
2008	0.345
2009	0.352
2010	0.361
2011	0.366
2012	0.37
2013	0.345
2014	0.347
2015	0.352