Year	Percent
1977	41.24236
1978	42.71892
1979	28.01003
1980	21.99662
1981	34.56569
1982	41.22545
1983	41.14921
1984	35.61565
1985	36.54294
1986	53.32783
1987	53.23035
1988	54.64358
1989	47.14206
1990	54.54384
1991	51.16179
1992	51.98262
1993	48.56134
1994	49.058
1995	49.81319
1996	51.34398
1997	55.80085
1998	58.66092
1999	58.56965
2000	43.029
2001	35.33712
2002	36.47296
2003	33.82282
2004	34.81541
2005	34.9
2006	37.0019
2007	35.08608
2008	34.20713
2009	30.25086
2010	35.56843
2011	37.57751
2012	32.58486
2013	38.54083
2014	52.06705
2015	50.06175
2016	48.34686
2017	44.21013