Year	% of total
1971	0.1543810776526573
1972	0.15960528519420844
1973	0.17076681336903177
1974	0.18883159589708767
1975	0.20367060189016234
1976	0.21603326356456515
1977	0.22360844423530676
1978	0.2163016037206568
1979	0.26189978992439855
1980	0.30274550336341993
1981	0.35202662321834693
1982	0.3977224066863376
1983	0.4519747659634868
1984	0.42798067201281
1985	0.4272343070384102
1986	0.45643585804985937
1987	0.45732493080909276
1988	0.44522169180842625
1989	0.4426776392187009
1990	0.4788220826419683
1991	0.5129389395764009
1992	0.5853342613497727
1993	0.580269012606905
1994	0.6160526112517329
1995	0.6892401658031757
1996	0.6741468426814421
1997	0.7041034498373272
1998	0.717816181242966
1999	0.7781836771123423
2000	0.8163081517135615
2001	0.8668882962672427
2002	0.8697706338639076
2003	0.889464536358415
2004	0.9066246552790669
2005	0.9688499399636776
2006	1.0229053107487314
2007	1.1386231716508974
2008	1.3575050662901684
2009	1.6926338542331398
2010	1.9705033477221583
2011	2.2830711257023446
2012	2.7059173604298894
2013	3.295195938511073
2014	3.7876783966350662
2015	4.4359978210830935