Year	Percent
1991	20.1
1992	22.185
1993	23.054
1994	24.093
1995	23.753
1996	22.457
1997	22.065
1998	22.196
1999	22.149
2000	21.974
2001	22.046
2002	22.333
2003	24.028
2004	26.997
2005	27.843
2006	27.692
2007	28.979
2008	28.875
2009	28.646
2010	28.165
2011	28.252
2012	28.14
2013	28.602
2014	28.692
2015	28.46
2016	28.25
2017	28.463
2018	28.473
2019	28.608
2020	28.6
2021	28.592
2022	28.578