Year	Percent
1981	9.3537
1982	9.43655
1983	9.622
1984	9.39744
1985	9.7123
1986	11.16385
1987	14.83671
1988	16.15315
1989	16.21903
1990	17.29625
1991	17.0091
1992	18.20837
1993	18.6389
1994	20.04756
1995	21.32721
1996	22.54736
1997	23.86325
1998	26.36789
1999	25.2463
2000	30.04857
2001	36.24588
2002	40.28048
2003	42.92986
2004	43.14182
2005	47.3057
2006	36.60867
2007	43.86477
2008	74.62271
2009	38.13459
2010	48.2085
2011	35.79053
2012	33.96867
2013	36.59888
2014	38.81915
2015	37.86072
2016	40.57046