Year	% of total
1971	1.159710308116258
1972	2.250126518340907
1973	2.361572958702701
1974	2.325913081088526
1975	2.6980721115655273
1976	2.4471471980011037
1977	2.1818485783980317
1978	1.978713807154768
1979	1.352963226872715
1980	1.379923655891806
1981	1.4328758621639779
1982	1.2150232421488287
1983	1.2728071063677961
1984	1.0417505940715786
1985	0.8832920763129276
1986	1.484879720578053
1987	1.7826702180545273
1988	1.6216847302432817
1989	1.1601729241552186
1990	1.2122871639849409
1991	0.9765492337777787
1992	0.8320457975191489
1993	1.1712740456627966
1994	1.2644430180678412
1995	2.416992210006318
1996	2.26389169619615
1997	2.2931686042291792
1998	2.5199861239865817
1999	2.276285234347009
2000	2.6799050577347177
2001	3.2956302380114257
2002	3.063133436983203
2003	2.958318055241218
2004	2.920236192912758
2005	2.8103559640680644
2006	2.658812998268383
2007	2.4321966034524536
2008	2.1214838688890776
2009	1.9083399129858736
2010	1.7539522606836628
2011	1.8412781633833246
2012	1.791542614408847
2013	1.7593591882440374
2014	2.205275187451047
2015	2.316686766235009