Year	% of total
1970	38.95555475263397
1971	37.933567161538406
1972	37.57508470416941
1973	38.059162525799515
1974	38.11424735572444
1975	38.13440767362883
1976	38.54896737700902
1977	38.94899201901063
1978	39.622511135628116
1979	40.13621088197334
1980	40.65162581350709
1981	40.96560225678981
1982	41.449372665271575
1983	41.139675707745205
1984	40.684194142976466
1985	41.06905444205742
1986	40.91464377681528
1987	40.46192785678469
1988	41.894585865597186
1989	42.52043350797871
1990	62.1308293552956
1991	61.650432900432904
1992	62.86076386888646
1993	62.58673158855752
1994	61.631731699451784
1995	61.33629979837308
1996	62.94694348327566
1997	64.77726690284163
1998	67.24956480455768
1999	69.26997569199405
2000	68.42819577572314
2001	69.38847649346059
2002	68.75056058839358
2003	70.22659256092348
2004	69.62373234764478
2005	69.1299044521244
2006	68.71573175875159
2007	68.77466140556682
2008	68.76055386693685