Year	% of total
1970	63.255315163723004
1971	71.23859871076573
1972	67.11991247117894
1973	61.173862382772356
1974	70.72585856480275
1975	71.20702556026293
1976	71.5568279342161
1977	64.09609200721438
1978	61.064600210967654
1979	64.03349514563106
1980	60.98230778672177
1981	62.986973280453505
1982	63.31929085921747
1983	53.25407119917385
1984	63.41283463756178
1985	66.25583645204817
1986	62.83834834520318
1987	57.38852072065384
1988	60.86407501063825
1989	67.56980474811286
1990	88.62629246676515
1991	87.95731707317073
1992	88.1159420289855
1993	88.01711840228246
1994	87.80141843971631
1995	87.46478873239437
1996	85.81661891117479
1997	85.97168597168597
1998	85.54216867469879
1999	83.8909541511772
2000	82.92682926829268
2001	83.27272727272728
2002	84.58942632170978
2003	85.99585062240665
2004	87.02439024390245
2005	87.58231420507995
2006	87.46492048643593
2007	87.63537906137185
2008	88.16013628620102