Year	%
1980	96.58646
1981	96.39617
1982	96.28634
1983	96.68149
1984	97.00447
1985	97.40943
1986	97.32474
1987	97.27446
1988	97.35334
1989	97.41486
1990	97.32859
1991	97.41835
1992	97.30277
1993	97.1535
1994	96.84037
1995	97.23022
1996	97.32247
1997	97.25121
1998	97.52574
1999	97.64104
2005	97.4514
2006	97.35165
2009	97.48661
2012	97.64374
2013	97.39809