Year	% of total
1970	7.387154207124263
1971	7.294705066795758
1972	7.001960034965511
1973	7.107348233445955
1974	7.1365468555897
1975	8.383058255728256
1976	9.078336664723905
1977	8.481511412156195
1978	8.535887835969417
1979	7.824027395049985
1980	7.015104121629288
1981	7.430662033291811
1982	6.538914314975431
1983	7.078560765801921
1984	6.934015940007478
1985	6.836379709238923
1986	6.4187333524940655
1987	6.41600261039499
1988	6.807997899580043
1989	6.990789285790659
1990	12.048192771084338
1991	12.075471698113208
1992	11.870503597122301
1993	11.643835616438356
1994	12.286689419795222
1995	12.416107382550337
1996	13.513513513513514
1997	14.144736842105262
1998	14.950166112956811
1999	14.906832298136646
2000	15.548780487804878
2001	15.43026706231454
2002	15.976331360946746
2003	15.217391304347828
2004	15.425531914893616
2005	14.86146095717884
2006	15.443037974683543
2007	15.233415233415235
2008	16.535433070866144