Year	% of total
1960	10.115036021380433
1961	12.313998540064011
1962	18.585138785127292
1963	17.583024810742113
1964	18.12796208530806
1965	20.969785575048736
1966	21.03760761214318
1967	22.009686215457243
1968	21.111154461394406
1969	19.172581917258196
1970	18.08216535939308
1971	15.911531651815517
1972	16.2864736171862
1973	16.661160385270275
1974	16.200231837429914
1975	15.64924641041648
1976	13.68714527531614
1977	13.753565316600113
1978	15.060032610306834
1979	16.986618356752476
1980	16.32608458092012
1981	16.640890813485925
1982	17.02032960423433
1983	18.654849075488595
1984	18.906602913788323
1985	18.934858595487768
1986	16.457729032579334
1987	15.994368684157154
1988	16.176646206023552
1989	24.380604955160358
1990	19.78563615988046
1991	19.333459629500176
1992	19.208215764770845
1993	18.31976298906359
1994	17.469939873611878
1995	18.585033603027533
1996	19.258272509813544
1997	18.848986914068092
1998	19.068164129502573
1999	19.380258273920163
2000	21.13713431127757
2001	21.672816908767896
2002	23.72975562072336
2003	25.058133660933663
2004	25.52796494362491
2005	24.4229205115752
2006	26.24655800404705
2007	25.382164961830412
2008	24.855809471942354
2009	26.752836105336105
2010	26.49023158613042
2011	27.198289046906186
2012	28.25751097335192
2013	30.305469075894948
2014	30.244429001570953
2015	31.337761907784756
2016	31.628401043296815