Year	% of total
1990	12.818342508398253
1991	14.441497567189169
1992	17.501900905002707
1993	18.223959886430595
1994	17.96435209749814
1995	19.32019776846508
1996	19.97459418143281
1997	20.87580216872341
1998	22.298443196956846
1999	22.31515630427111
2000	22.526723644605962
2001	21.547919671546822
2002	22.62770206817951
2003	22.233576572063825
2004	23.662172425855783
2005	21.999150090793353
2006	22.69052908375065
2007	21.627850171956954
2008	20.684829027564305
2009	22.695585059200937
2010	24.607244720239255
2011	23.553769002402795
2012	21.773914516287174
2013	21.939583917686246
2014	22.079321054217075
2015	23.984519107654354
2016	22.233657681764598