Year	% of total
1990	3.492445244945333
1991	3.6684625806110236
1992	3.893433453432193
1993	4.193689392161031
1994	4.373319593557086
1995	4.627568136077272
1996	4.975131511617259
1997	5.06170145380045
1998	4.288918263103405
1999	5.458167162873616
2000	4.865065789698245
2001	5.257625129111927
2002	4.745300935208253
2003	4.657665716235334
2004	4.293846274770204
2005	4.09060009453767
2006	4.142198202817695
2007	4.243868572889253
2008	4.43855488553273
2009	4.558637941766676
2010	4.610633959146387
2011	4.689321631090007
2012	4.948452276590686
2013	5.151115385845721
2014	5.450781658820164
2015	5.928622439039866
2016	6.127077574598723