Year	Percent
1978	16.82752
1979	14.13748
1980	17.9858
1981	19.51782
1982	21.80929
1983	28.77364
1984	26.22429
1985	42.68077
1986	56.32928
1987	59.92264
1988	48.88499
1989	43.8979
1990	58.11899
1991	56.18195
1992	36.45318
1993	58.97052
1994	53.44938
1995	49.49249
1996	43.56324
1997	24.97646
1998	33.31738
1999	34.81971
2000	35.86811
2001	40.70568
2002	53.19582
2003	54.61667
2004	47.42142
2005	40.28472
2006	37.84314
2007	37.18412
2008	32.47198
2009	39.83825
2010	46.47261
2011	38.29061
2012	24.4945
2013	19.40075
2014	17.03433
2015	18.50566
2016	20.83121