Year	Percent
1991	52.9
1992	47.06
1993	42.84
1994	40
1995	36.85
1996	35.47
1997	37.93
1998	42.44
1999	41.94
2000	41.14
2001	42.43
2002	42.27
2003	38.89
2004	36.74
2005	35.48
2006	35.09
2007	34.8
2008	34.49
2009	31.13
2010	28.04
2011	26.56
2012	22.83
2013	21.45
2014	22.21
2015	22.84
2016	24.09
2017	26.16
2018	27.6
2019	28.26