Year	Percent
1991	31.014
1992	31.502
1993	31.228
1994	30.956
1995	31.652
1996	30.819
1997	30.964
1998	31.275
1999	28.718
2000	29.369
2001	29.379
2002	29.623
2003	29.959
2004	30.052
2005	30.306
2006	30.617
2007	31.593
2008	32.854
2009	32.582
2010	32.89
2011	29.412
2012	30.507
2013	30.806
2014	31.064
2015	31.039
2016	31.415
2017	29.576
2018	30.105
2019	30.689
2020	31.165
2021	31.694
2022	32.443