Year	Percent
1990	28.8356
1991	35.28017
1992	27.03394
1993	33.71966
1994	16.77559
1995	36.68308
1996	27.68728
1997	27.0404
1998	22.49654
1999	18.14566
2000	24.58799
2001	28.07562
2002	30.81147
2003	37.27249
2004	40.20774
2005	37.85425
2006	36.50142
2007	39.67031
2008	41.14461
2009	34.24142
2010	31.65989
2011	32.65564
2012	27.33479
2013	26.60046
2014	23.08082
2015	19.51832
2016	18.93016
2017	28.51983