Year	% of total
1991	16.644575060676416
1992	16.57146255843051
1993	17.19550154109119
1994	17.063240271613104
1995	18.247118643473133
1996	19.277069742534977
1997	19.143173880577418
1998	19.745647612270158
1999	20.518274930617693
2000	21.020944368185937
2001	21.418761119965733
2002	21.615477543686463
2003	22.128091249645625
2004	22.675456564530823
2005	23.601065964101227
2006	23.519829747746083
2007	23.38603782754048
2008	24.345394561214974
2009	24.70948649303871
2010	25.842326904497455
2011	24.513697632462065
2012	24.525552155817497
2013	24.688569462677233
2014	22.878244608670133
2015	20.950608023391773
2016	22.001997538336298