Year	Percent
1980	33.15304
1981	38.37416
1982	42.76501
1983	54.22643
1984	57.67601
1985	48.73437
1986	34.76277
1987	35.7779
1988	35.51444
1989	37.39711
1990	47.0823
1991	42.65396
1992	45.60946
1993	46.00079
1994	45.31599
1995	44.64783
1996	45.96035
1997	52.13828
1998	42.28952
1999	37.37858
2000	39.17897
2001	37.95624
2002	42.31001
2003	43.27764
2004	45.59959
2005	45.38333
2006	41.27085
2007	40.79479
2008	45.16208
2009	49.11009
2010	46.62652
2011	44.33988
2012	49.0879
2013	47.82396
2014	48.55579