Year	% of total
1991	38.7299494528291
1992	39.050128949634626
1993	37.695897540865076
1994	36.96977856226889
1995	35.95441146786348
1996	35.053175717487804
1997	34.57700978698586
1998	33.085951767565376
1999	31.96314589372233
2000	32.56419199910187
2001	32.067107117530746
2002	32.07371261474034
2003	31.97480664928771
2004	31.658722132537466
2005	30.848901219750072
2006	31.71564922244477
2007	32.22752272707596
2008	30.712618432626797
2009	29.464173823721833
2010	30.349591116622623
2011	31.776597811875206
2012	32.14547341102414
2013	32.24277045751751
2014	32.29749206070294
2015	37.39751572338332
2016	35.789423900406966