Year	%
1979	96.899
1980	97.22311
1981	97.00872
1982	96.89851
1983	97.29801
1984	97.52605
1985	97.75862
1986	97.57117
1987	97.26495
1988	97.09359
1989	97.05635
1990	97.22346
1991	97.4253
1992	97.8392
1993	97.71776
1994	97.56197
1995	97.58238
1996	97.69915
1997	97.66675
1998	97.64539
1999	97.72053
2000	98.11299
2001	98.05127
2002	98.08027
2003	98.09821
2004	98.17373
2005	98.20529
2006	98.17473
2007	98.21313
2008	98.27507
2009	98.27107
2010	98.26278
2011	98.19528
2012	98.30281
2013	98.34952
2014	97.90123
2015	98.21004
2016	98.26045
2017	98.24901