Year	Percent
1981	36.87117
1982	36.17486
1983	38.50242
1984	38.10559
1985	33.19767
1986	36.67575
1987	33.41004
1988	32.00927
1989	28.97638
1990	30.05229
1991	33.5403
1992	33.90136
1993	38.63654
1994	36.7523
1995	36.2223
1996	34.42151
1997	38.66597
1998	36.18775
1999	35.68796
2000	24.08996
2001	16.51175
2002	20.06674
2003	26.40641
2004	30.93033
2005	34.07129
2006	36.13789
2007	41.64978
2008	44.3
2009	39.3
2010	49.33461
2011	58.10791
2012	59.70601
2013	52.93032
2014	50.76278
2015	45.07474