Year	% of total
1971	10.782838396740528
1972	13.086092937379759
1973	17.51964089999846
1974	19.414605696959043
1975	20.992530299621986
1976	21.639553209997185
1977	19.934471449903388
1978	17.983287345025197
1979	21.529878792880716
1980	23.154217671808585
1981	22.538870316337103
1982	25.656996816138722
1983	21.771700503659673
1984	23.940185446117866
1985	23.67968400686962
1986	23.435865448264575
1987	29.733403862870638
1988	31.98010160651714
1989	35.08812901566014
1990	40.09332330744399
1991	41.49362807144995
1992	42.54647891060653
1993	45.25142262238171
1994	48.11637170237981
1995	48.07337270379294
1996	48.51244754457004
1997	49.28071905057214
1998	51.41283398975736
1999	54.84029494145448
2000	54.13078542321138
2001	56.72750831453142
2002	57.37297548635206
2003	60.42781522442816
2004	60.48967587040172
2005	62.440523458467304
2006	62.376471644211684
2007	62.779488449151046
2008	65.64031627456018
2009	66.21509913580168
2010	65.95635934987666
2011	63.42658678025338
2012	62.74214364386258
2013	59.0773628550194
2014	62.25518293734908
2015	66.34160450324816