Year	Percent
1988	42.34199
1989	43.58341
1990	41.13737
1991	38.38011
1992	36.58951
1993	40.14664
1994	40.86446
1995	45.95738
1996	46.76703
1997	46.45531
1998	44.43145
1999	47.07237
2000	47.83989
2001	47.63195
2002	40.79819
2003	34.67451
2004	34.04294
2005	34.73374
2006	34.52714
2007	27.25763
2008	25.72634
2009	24.26009
2010	20.75363
2011	21.19138
2012	21.98552
2013	21.74606
2014	20.372
2015	26.75199
2016	29.08979