Year	% of total
1970	78.29264376624744
1971	79.13933116100935
1972	79.51650724241598
1973	80.60875044602524
1974	80.51477004327735
1975	81.47759477590319
1976	79.62884530010653
1977	81.64475304706545
1978	80.49293151318834
1979	80.20671007314364
1980	79.5948020194089
1981	80.52135399471773
1982	80.87097389669285
1983	80.54035882652197
1984	81.35449238953746
1985	80.60407615982837
1986	80.73880261649992
1987	80.05741737077916
1988	80.37842771533778
1989	79.28109048305694
1990	81.9327731092437
1991	81.34171907756813
1992	81.28772635814889
1993	81.53846153846153
1994	82.80961182994456
1995	81.78633975481611
1996	80.73701842546063
1997	79.6116504854369
1998	78.1150159744409
1999	77.33537519142419
2000	76.23318385650224
2001	77.37556561085974
2002	78.796992481203
2003	79.3103448275862
2004	82.21574344023324
2005	82.58859784283513
2006	83.13253012048193
2007	80.55555555555556
2008	78.96725440806046