Year	Percent
1991	25.979
1992	25.832
1993	25.636
1994	25.366
1995	24.967
1996	24.86
1997	24.613
1998	24.283
1999	23.949
2000	23.65
2001	23.408
2002	23.196
2003	22.393
2004	21.655
2005	20.934
2006	20.358
2007	21.265
2008	22.239
2009	23.241
2010	24.234
2011	25.263
2012	26.277
2013	27.324
2014	28.334
2015	29.364
2016	29.203
2017	29.362
2018	29.524
2019	29.688
2020	29.991
2021	30.273
2022	30.546