Year	% of total
1971	12.459788200156027
1972	11.636615827743881
1973	11.18642651469913
1974	10.194887924868146
1975	10.796628841673833
1976	9.811368053249895
1977	9.914030692987511
1978	9.772768193747867
1979	10.34101152067361
1980	10.023194722846974
1981	9.366247032360416
1982	10.043588937145714
1983	9.906080595418839
1984	9.82226113764268
1985	9.48500284008465
1986	9.378758427230622
1987	8.888713846448477
1988	10.086409980884405
1989	10.036763945744537
1990	10.140502617067161
1991	10.766031003530644
1992	10.469394028921416
1993	10.544111996518119
1994	10.33088052524042
1995	11.04001577984796
1996	11.204919044473565
1997	11.206061229176155
1998	12.484990650247276
1999	13.256111842230425
2000	14.32616304446562
2001	16.58281545103796
2002	17.89226677797655
2003	19.893692636123617
2004	20.995109754093257
2005	19.939517097595186
2006	20.231172853876238
2007	20.6468033172225
2008	22.250217956627846
2009	21.823769260659343
2010	23.52216688513603
2011	22.39000750336873
2012	24.14419071110618
2013	25.508100174058185
2014	26.554798270948993
2015	27.869797253454543