Year	Percent
1990	34.84
1991	36.34
1992	37.95
1993	39.71
1994	41.59
1995	40.73
1996	39.79
1997	38.85
1998	37.89
1999	36.94
2000	36
2001	35.19
2002	34.34
2003	33.53
2004	32.75
2005	31.96
2006	31.19
2007	30.43
2008	29.7
2009	28.94
2010	28.19
2011	27.56
2012	26.91
2013	26.27
2014	25.66
2015	25.06
2016	24.39
2017	23.73
2018	23.06
2019	23.05