Year	% of total
1970	16.924553248558833
1971	17.357007111159113
1972	17.380830599995694
1973	15.791123151172709
1974	20.40457715500315
1975	18.74215975570592
1976	18.1167353699575
1977	15.52700241790581
1978	18.304604823171704
1979	16.84612831926552
1980	13.541506577906
1981	16.40587451333785
1982	14.40214768566026
1983	15.390186356596613
1984	15.554041672279439
1985	17.386573020425725
1986	17.92462827499387
1987	17.276615515725982
1988	18.557264299884253
1989	17.24232106653389
1990	28.14814814814815
1991	27.857142857142858
1992	27.972027972027973
1993	28.373702422145332
1994	27.36156351791531
1995	29.794520547945208
1996	27.217125382262996
1997	27.083333333333332
1998	26.285714285714285
1999	27.728613569321535
2000	26.08695652173913
2001	31.024096385542173
2002	30.303030303030305
2003	32.40997229916898
2004	34.065934065934066
2005	32.26600985221675
2006	35.07462686567165
2007	36.19047619047619
2008	38.80952380952381