Year	% of total
1970	33.425256076864784
1971	34.62956463771179
1972	35.75211481270789
1973	35.56228879698173
1974	38.22007986173704
1975	42.93386274915853
1976	42.62744552270096
1977	43.593134490671375
1978	44.35612014382217
1979	43.562007724410236
1980	44.32988583776806
1981	45.37798773145733
1982	45.86961470054166
1983	46.10219239655367
1984	45.9951051531059
1985	47.078770356319794
1986	46.664193325698164
1987	46.60177080265592
1988	46.59052676551655
1989	46.00229041829814
1990	36.55068584810974
1991	36.13203012337766
1992	35.22392685572602
1993	33.78235205085515
1994	33.56602675974404
1995	32.83497884344146
1996	31.971654856190078
1997	31.6804781958973
1998	31.543357199681783
1999	31.136481577581733
2000	31.048029400582944
2001	32.37364043506078
2002	33.14218688909162
2003	34.505465560384565
2004	35.62266167824693
2005	37.140930546190155
2006	37.29020032485111
2007	37.839297771775826
2008	38.25910931174089