Year	Percent
1980	46.12729
1981	41.61364
1982	36.27809
1983	43.85502
1984	42.58086
1985	35.64926
1986	26.62717
1987	25.45868
1988	20.1997
1989	24.63688
1990	16.42983
1991	28.59941
1992	29.4167
1993	18.3041
1994	19.63313
1995	14.60853
1996	14.40527
1997	17.44649
1998	21.42273
1999	7.9052
2000	16.57502
2001	15.70951
2002	23.25411
2003	23.73586
2004	20.52001
2005	26.7353
2006	30.38747
2007	34.71326
2008	35.17118
2009	26.14331
2010	27.28639
2011	22.40296
2012	28.14455
2013	25.94225
2014	26.8445
2015	26.5241
2016	29.5744