Year	% of total
1971	0
1972	0.025374270489723422
1973	1.8863322221318806
1974	3.771534999223964
1975	1.3987583214900143
1976	3.044706206516498
1977	0.7447573005814333
1978	0.12312078797304302
1979	12.747135308436738
1980	22.652376421094804
1981	26.049226084750067
1982	29.569620253164558
1983	31.977953410981698
1984	36.29117160475259
1985	42.75233538391433
1986	49.3741834885583
1987	49.792405501254215
1988	51.013693757780544
1989	51.95299145299145
1990	47.20555359454053
1991	48.18020691645027
1992	47.563705234159784
1993	47.77075361836633
1994	49.47364286275434
1995	43.27607083396398
1996	44.19344700243577
1997	44.19829960483774
1998	44.27949634696098
1999	46.67141078099982
2000	53.55542567699201
2001	53.68847312908086
2002	55.73388799205266
2003	57.651842767701545
2004	55.8962573867367
2005	56.54184741005358
2006	57.63655563021983
2007	54.976337301018205
2008	58.077190542420034
2009	54.32694162583434
2010	53.065831634139236
2011	54.47893099547512
2012	54.698531488280146
2013	55.13081293399733
2014	57.090761750405186
2015	56.87143286272154