Year	Percent
1975	22.76498
1976	21.96025
1977	21.39503
1978	22.0217
1979	21.8
1980	23.36739
1981	19.42523
1982	16.92558
1983	16.44292
1984	20.56114
1985	22.20577
1986	24.04941
1987	24.01571
1988	23.74035
1989	23.34228
1990	22.86685
1991	23.88347
1992	27.22726
1993	30.71962
1994	34.59998
1995	38.23634
1996	36.13007
1997	37.59527
1998	43.39308
1999	37.40858
2000	38.15975
2001	34.95891
2002	31.8348
2003	32.39706
2004	34.4698
2005	33.54865
2006	35.95617
2007	37.78537
2008	41.46685
2009	21.83656
2010	35.19329
2011	40.56372
2012	30.23806
2013	27.16639
2014	25.6776
2015	23.45935
2016	24.65789
2017	24.12343