Year	Percent
1991	49.92
1992	48.87
1993	47.7
1994	46.56
1995	45.4
1996	44.16
1997	42.9
1998	41.63
1999	40.39
2000	39.37
2001	38.51
2002	37.65
2003	36.87
2004	36.17
2005	35.48
2006	34.79
2007	34.04
2008	33.2
2009	32.07
2010	31.16
2011	30.34
2012	29.52
2013	28.64
2014	27.72
2015	26.64
2016	25.64
2017	24.58
2018	25.59
2019	24.9