Year	% of total
1971	43.65431582096412
1972	45.37713215634129
1973	49.29393185498502
1974	50.81095862769024
1975	52.110199226457034
1976	54.14728920656111
1977	54.12207260964295
1978	56.3716066336697
1979	56.34683558167259
1980	54.80135232370922
1981	52.90703672471214
1982	52.55057472036528
1983	49.65340269968107
1984	47.40273205184947
1985	48.213363200438266
1986	50.00810055425487
1987	49.50270933071273
1988	49.979240165652755
1989	49.83301128321505
1990	51.215830268381794
1991	51.95474510803514
1992	52.68438588108568
1993	53.26424996673255
1994	53.266728950637365
1995	54.60825220906822
1996	56.26743392524539
1997	56.681184017130995
1998	57.340508135754675
1999	57.28867438512134
2000	58.23206391597715
2001	58.94968976927365
2002	57.153997606778276
2003	54.641328441339134
2004	54.698224295968565
2005	54.25232116377915
2006	53.42289187732524
2007	52.66064025531939
2008	52.569460611017185
2009	51.31850799199577
2010	53.48790284377864
2011	54.56870942445757
2012	56.548892266276795
2013	58.01808225265142
2014	59.10753263897526