Year	Percent
1991	20.622
1992	20.919
1993	20.466
1994	20.274
1995	20.211
1996	19.549
1997	19.255
1998	18.701
1999	17.216
2000	16.595
2001	17.468
2002	17.587
2003	18.388
2004	19.271
2005	20.296
2006	22.634
2007	23.612
2008	24.974
2009	21.904
2010	19.118
2011	25.362
2012	21.77
2013	23.099
2014	23.841
2015	27.622
2016	30.805
2017	31.07
2018	31.279
2019	31.435
2020	31.589
2021	31.717
2022	31.919