Year	% of total
1971	27.135493902702386
1972	26.87788659928071
1973	28.21531507837305
1974	27.252582666002784
1975	27.78357169945608
1976	29.12905601957626
1977	31.010984084286036
1978	30.38439419383037
1979	30.618626323132485
1980	29.699727666690546
1981	28.342262092001974
1982	32.010521426602125
1983	28.989132786097098
1984	30.42804752329673
1985	27.224833162185597
1986	28.650841653445063
1987	29.121254994995194
1988	30.648199870995786
1989	31.77469907420148
1990	30.0164945420926
1991	29.869868009993294
1992	32.282749022953794
1993	33.224253736884855
1994	36.951679832299135
1995	41.23647125979289
1996	40.3233855674219
1997	38.1099302309588
1998	42.86878070534983
1999	49.089648525080456
2000	48.27216357524626
2001	52.812552218497544
2002	53.55272814278192
2003	54.73352652619068
2004	56.48111791082429
2005	54.86179356322117
2006	50.476523866006914
2007	54.82596041673374
2008	54.277914486857945
2009	50.800484915280066
2010	51.16665965535919
2011	52.14850778610391
2012	51.484883627671785
2013	51.35134251473604
2014	52.47931252849074