Year	Percent
1980	10.8619
1981	9.94958
1982	8.31367
1983	6.11708
1984	4.14566
1985	2.8596
1986	2.52469
1987	6.64118
1988	8.07092
1989	8.22347
1990	8.17407
1991	9.17376
1992	10.60872
1993	9.39291
1994	11.99871
1995	13.21453
1996	13.17561
1997	12.00688
1998	10.93093
1999	10.16577
2000	12.83173
2001	21.11704
2002	24.41042
2003	25.56425
2004	28.92505
2005	30.19046
2006	30.21688
2007	30.83728
2008	29.33718
2009	29.96951
2010	31.51022
2011	33.42669
2012	32.37613
2013	30.36931
2014	33.3593
2015	32.21628
2016	36.67764
2017	38.26649