Year	% of total
1970	8.712527132985803
1971	9.256132404655434
1972	9.255333180119118
1973	9.2174660248081
1974	8.574853456849176
1975	8.39357473042592
1976	8.385518260855768
1977	8.367245490584086
1978	8.595152144256554
1979	8.622055313071494
1980	8.916089619634397
1981	9.389447001171835
1982	10.041659674137367
1983	10.353474370050629
1984	10.890084092565795
1985	11.439022464447902
1986	12.098442616674536
1987	12.566966726825587
1988	13.218464025597223
1989	13.430191246056783
1990	11.524163568773234
1991	12.313432835820896
1992	12.830188679245284
1993	12.260536398467432
1994	12.260536398467432
1995	12.692307692307692
1996	13.513513513513514
1997	13.94422310756972
1998	14.000000000000002
1999	14.522821576763487
2000	14.285714285714285
2001	13.692946058091287
2002	13.973799126637553
2003	13.716814159292035
2004	11.659192825112108
2005	11.45374449339207
2006	10.964912280701753
2007	10.714285714285714
2008	10.822510822510822