Year	Percent
1990	27.88
1991	27.9
1992	27.83
1993	28
1994	28.24
1995	29.47
1996	30.74
1997	32.05
1998	33.39
1999	34.75
2000	36.15
2001	37.58
2002	39.03
2003	38.41
2004	40.65
2005	42.39
2006	33.65
2007	35.35
2008	37.1
2009	38.92
2010	34.52
2011	34.12
2012	40.01
2013	36.79
2014	35.02
2015	33.02
2016	33.83
2017	37.54
2018	37.43
2019	38.59