Year	% of total
1990	33.372688698958505
1991	33.605084614151146
1992	31.137454276390013
1993	32.183995289236435
1994	32.248679627865634
1995	31.93636822993896
1996	32.24637874009868
1997	32.0514289135074
1998	31.099762398848384
1999	31.501703499231144
2000	31.43398675831535
2001	31.1523090455479
2002	30.62157612317961
2003	31.348354905294293
2004	31.81753494639218
2005	32.137909758238976
2006	32.71349161255292
2007	33.18751855017784
2008	34.49234671611836
2009	34.69539575208638
2010	32.720328560686376
2011	34.489613565139095
2012	35.3400313222227
2013	32.610793736055925
2014	33.5254572471607
2015	34.506681308323536
2016	35.79149648268662