Year	% of total
1971	0.19598504951958362
1972	0.20462049143761762
1973	0.24193103200481317
1974	0.29266880204762535
1975	0.3690545641448025
1976	0.422449493105327
1977	0.6162350068919562
1978	0.753119357714787
1979	0.8767605289716627
1980	0.8136212365526276
1981	0.8819332482379952
1982	0.8246498194879843
1983	0.9788229974953707
1984	0.9934394587798436
1985	0.9980625429044389
1986	1.1174590249538237
1987	1.3416306888329455
1988	1.4485699591941747
1989	1.7144139423615412
1990	1.889019983481454
1991	1.753226504486257
1992	2.005520751508813
1993	2.1258952267291975
1994	2.8824891182421606
1995	3.5795905250770836
1996	5.4145474119980985
1997	6.232227912995378
1998	6.629170898466151
1999	6.855406318296763
2000	6.3759587587032
2001	5.825803981289498
2002	6.391913831695654
2003	6.728591899419278
2004	7.167324354706875
2005	8.51768941936612
2006	8.026448493311214
2007	8.01531059640955
2008	8.209566572668582
2009	8.36732386667556
2010	10.184931365315254
2011	11.17216750197066
2012	10.870637953049414
2013	11.283711577818815
2014	12.20548476059432
2015	14.025760781412867