Year	% of total
1991	32.65391053863388
1992	31.396357783941795
1993	29.736571572830147
1994	29.748442539694473
1995	28.68794951050883
1996	27.58149218922671
1997	27.14319067606338
1998	26.332063436038908
1999	25.513099351912746
2000	26.348383181095077
2001	25.75783216483964
2002	25.976815837336034
2003	25.85855043747785
2004	25.943640804610336
2005	24.977532624234797
2006	25.404369615251465
2007	26.08866433312978
2008	24.36942770558132
2009	23.105424399556387
2010	23.928880418161157
2011	25.273075880372073
2012	26.538795080683315
2013	26.257769845878183
2014	26.649730072413785
2015	32.01950397053317
2016	30.09753137996508