Year	% of total
1990	3.1936025981163993
1991	3.607726493739958
1992	3.6504256293401562
1993	3.9415521353333105
1994	3.8176259016260046
1995	3.7169568739081873
1996	3.840550889985281
1997	3.929839903727995
1998	3.9179334811597584
1999	4.476833718324642
2000	4.9543050095001515
2001	4.4954971551033465
2002	4.416090602606429
2003	5.536350451013215
2004	6.121242831410037
2005	6.077408147743813
2006	6.06195753814936
2007	6.053515590552566
2008	5.866786142816643
2009	5.68089507085532
2010	6.043194758617872
2011	7.139594241646619
2012	7.033813240463192
2013	6.826173773617351
2014	7.274091089827057
2015	7.7539570359599
2016	7.713242082821885