Year	Percent
1991	16.905
1992	17.091
1993	17.424
1994	17.935
1995	18.471
1996	18.431
1997	18.841
1998	18.612
1999	18.343
2000	18.14
2001	18.392
2002	18.536
2003	18.64
2004	19.142
2005	18.216
2006	19.408
2007	21.179
2008	21.228
2009	21.63
2010	22.611
2011	22.129
2012	23
2013	23.077
2014	22.396
2015	22.815
2016	22.148
2017	21.647
2018	21.784
2019	21.885
2020	21.998
2021	22.127
2022	22.256