Year	%
1971	89.09305
1972	88.30669
1973	86.94351
1974	85.61045
1976	83.52576
1977	82.60611
1978	82.66617
1979	80.89056
1980	81.76459
1981	82.62925
1982	83.63551
1983	84.32155
1984	84.34925
1985	83.44308
1986	80.739
1987	78.00734
1988	76.14332
1989	74.83412
1990	72.9429
1991	72.00284
1992	67.96068
1993	68.90938
1998	71.70455
1999	71.18434
2000	73.48891
2001	75.00706
2002	97.00685
2003	97.82214
2004	98.46182
2005	98.57143
2006	98.35326
2007	98.64779
2008	97.67975
2009	97.91369
2010	98.5093
2011	97.86927
2012	57.25702