Year	% of total
1970	55.69124654590099
1971	56.383350846713796
1972	55.60004672136171
1973	54.71729863971609
1974	56.4004238439864
1975	56.64232660495252
1976	56.85247537336365
1977	56.56993588045648
1978	58.08962764512028
1979	56.96069048337321
1980	56.822907918467294
1981	57.588576868032206
1982	55.0177370053193
1983	43.10207077545755
1984	43.11420053964115
1985	45.88261540713358
1986	41.51502422527399
1987	43.858535627881146
1988	54.675889839682036
1989	48.44472468893126
1990	66.99889258028793
1991	66.5929203539823
1992	66.30076838638858
1993	65.93886462882097
1994	65.6182212581345
1995	63.63636363636363
1996	62.41062308478039
1997	61.62109375
1998	62.0345140781108
1999	61.58536585365854
2000	62.809257781324824
2001	60.80525883319638
2002	59.9835661462613
2003	61.651234567901234
2004	58.76623376623377
2005	60.72782410917361
2006	58.177570093457945
2007	56.95517774343122
2008	54.060509554140125