Year	% of total
1971	12.823549006174042
1972	12.597256599329013
1973	13.795178297645819
1974	14.395028430240103
1975	15.039368150481502
1976	14.167271253758033
1977	14.188688937685647
1978	13.482134040010093
1979	12.778957108557723
1980	12.423189100179483
1981	12.025304341606107
1982	12.049692140468645
1983	11.888907950704303
1984	10.043729797209258
1985	9.634509429055441
1986	9.453992219631568
1987	9.235215531899392
1988	9.195580655125275
1989	9.156830149966542
1990	8.37770228391651
1991	11.243831656279312
1992	10.504516947744271
1993	10.46650289275282
1994	9.845835089856408
1995	10.598987725559757
1996	9.83861966685993
1997	9.762051807682278
1998	10.22561391481578
1999	10.644640699856204
2000	12.219677974105664
2001	11.862643000732046
2002	12.129643685669791
2003	11.347741508403265
2004	10.997582683071235
2005	12.005083263113862
2006	11.572732513050163
2007	11.418298257358202
2008	14.39817455423287
2009	14.59789927703664
2010	13.629102296523715
2011	12.245605355846951
2012	12.124396859938424
2013	12.501642307320756
2014	11.578447108322946
2015	11.839119126125528