Year	Percent
1981	2.96147
1982	4.07083
1983	4.15079
1984	4.62781
1985	5.38111
1986	7.88709
1987	12.95466
1988	13.59219
1989	12.91373
1990	15.28414
1991	15.6863
1992	16.95688
1993	19.36144
1994	17.83398
1995	16.33844
1996	15.13163
1997	15.43203
1998	14.2243
1999	13.7639
2000	12.17253
2001	13.94274
2002	12.72422
2003	12.51799
2004	12.60185
2005	12.48139
2006	11.76323
2007	10.48972
2008	8.21663
2009	8.77524
2010	12.09086
2011	13.92069
2012	13.32728
2013	15.44293
2014	16.86927
2015	12.03384
2016	12.7946