Year	%
1980	96.89188
1981	96.71002
1982	96.54446
1983	96.91626
1984	97.11196
1985	97.42813
1986	97.33318
1987	97.08813
1988	97.04
1989	97.19551
1990	97.46709
1991	97.55355
1992	97.53309
1993	97.46852
1994	97.15695
1995	97.31874
1996	97.47723
1997	97.26124
1998	97.35782
1999	97.3671
2005	97.71949
2006	97.69688
2009	97.83746
2012	98.15199
2013	98.29463