Year	Percent
1991	17.65
1992	17.209
1993	17.999
1994	17.518
1995	19.741
1996	20.721
1997	21.903
1998	22.031
1999	22.371
2000	22.513
2001	22.237
2002	22.769
2003	23.514
2004	26.148
2005	31.073
2006	35.125
2007	32.599
2008	33.308
2009	35.75
2010	38.462
2011	36.017
2012	39.223
2013	38.904
2014	37.466
2015	37.593
2016	38.936
2017	38.752
2018	39.891
2019	40.709
2020	40.056
2021	39.857
2022	40.595