Year	Percent
1979	18.13336
1981	15.43481
1984	14.82638
1985	14.05109
1987	12.50125
1988	12.10307
2000	37.89014
2001	43.77376
2002	43.49841
2003	46.89064
2004	48.83035
2005	50.27722
2006	55.8073
2007	58.87387
2008	60.52009
2009	61.26926
2010	64.15205
2011	64.5394
2012	59.06263
2014	56.4924
2015	53.65859
2016	54.0738