Year	Percent
1976	14.47033
1977	15.1337
1978	17.50028
1979	22.10442
1981	34.31079
1985	37.84564
1986	39.86196
1987	43.12903
1988	48.03283
1989	42.79989
1990	36.02307
1991	38.98368
1992	37.32821
1993	37.73172
1994	37.36999
1995	38.46872
1996	38.35932
1997	42.92037
1998	47.31173
1999	47.88724
2001	47.44443
2002	44.14837
2005	43.03094
2006	44.03038
2007	54.80077
2009	65.4983
2012	67.51178
2013	69.0906
2014	66.0979
2015	66.07627
2016	56.97895