Year	Percent
1990	37.12
1991	37.36
1992	37.61
1993	37.94
1994	38.31
1995	38.72
1996	39.16
1997	39.64
1998	40.15
1999	40.68
2000	41.21
2001	37.25
2002	33.47
2003	29.92
2004	26.59
2005	23.51
2006	20.62
2007	18
2008	15.65
2009	13.6
2010	14.88
2011	16.25
2012	17.84
2013	19.66
2014	21.74
2015	22.67
2016	23.67
2017	23.8
2018	24.63
2019	25.88