Year	Percent
1979	9.0105
1981	7.68898
1984	7.67032
1985	7.1787
1987	6.87999
1988	6.63777
2000	23.94299
2001	26.08369
2002	28.1932
2003	30.84785
2004	32.49871
2005	33.85065
2006	38.39298
2007	41.28324
2008	44.91991
2009	47.29002
2010	50.61125
2011	51.6467
2012	49.75213
2014	49.68231
2015	47.98511
2016	47.80508