Year	Percent
1981	23.87088
1982	26.25876
1983	26.60817
1984	29.17961
1985	26.72975
1986	30.17821
1987	30.8033
1988	28.44899
1989	22.48678
1990	18.2747
1991	54.06846
1992	28.93299
1993	59.33219
1994	44.63069
1995	40.54137
1996	35.52433
1997	52.66635
1998	47.84351
1999	50.15844
2000	53.99675
2001	50.31834
2002	50.72662
2003	52.35205
2004	60.78777
2005	58.76938
2006	59.44327
2007	59.61445
2008	54.01704
2009	50.278
2010	46.67898
2011	52.55356
2012	43.57215
2013	38.89024
2014	52.249
2015	45.64559
2016	50.21567
2017	59.47042