Year	Percent
1983	17.1174
1984	17.4152
1985	17.7382
1986	15.9863
1987	17.5443
1988	17.0383
1989	17.0094
1990	15.0985
1991	16.8876
1992	17.2396
1993	18.7676
1994	19.7752
1995	19.4235
1996	21.4889
1997	22.1683
1998	21.1441
1999	22.7838
2000	21.8575
2001	20.9883
2002	18.7264
2003	17.8442
2004	18.6549
2005	18.8947
2006	17.5816
2007	15.5105
2008	16.8801
2009	19.51
2010	26.8462
2011	38.844
2012	48.4719
2013	53.7713
2014	47.3869
2015	45.2305
2016	44.3219
2017	39.3251