Year	% of total
1970	23.813959672428677
1971	37.95336796313119
1972	36.56903921656456
1973	35.38563335601946
1974	39.73513515683506
1975	34.383223812789
1976	36.26688543960505
1977	34.93518501024302
1978	33.99648522073061
1979	27.351607507970105
1980	32.10696317424401
1981	35.344380044281536
1982	32.09678850172508
1983	32.97817180510045
1984	40.897120310764436
1985	40.567127408257356
1986	42.06230781462545
1987	33.71108754835162
1988	45.3550804657935
1989	41.746805747578044
1990	24.939349830179523
1991	26.153114598193056
1992	27.34047508150908
1993	28.617363344051448
1994	29.711451758340846
1995	30.943900267141583
1996	33.52059925093633
1997	34.3735444806707
1998	32.81452658884565
1999	34.97536945812808
2000	34.869565217391305
2001	36.757425742574256
2002	37.4141876430206
2003	36.54371584699454
2004	38.301387970918704
2005	40.115718418514945
2006	44.32328415651058
2007	45.07587027670336
2008	48.2728337236534