Year	% of total
1990	3.1936025981163993
1991	3.6077264937399574
1992	3.6504256293401554
1993	3.9415521353333105
1994	3.817625901626004
1995	3.716956873908187
1996	3.840550889985281
1997	3.929839903727996
1998	3.9179334811597584
1999	4.476833718324642
2000	4.9543050095001515
2001	4.4954971551033465
2002	4.416090602606429
2003	5.536350451013216
2004	6.121242831410038
2005	6.077408147743812
2006	6.061957538149361
2007	6.053515590552566
2008	5.866786142816644
2009	5.680895070855321
2010	6.043194758617872
2011	7.139594241646619
2012	7.033813240463194
2013	6.8261737736173504
2014	7.274091089827059
2015	7.7539570359599
2016	7.713242082821883