Year	Percent
1991	32.185
1992	31.701
1993	31.214
1994	30.985
1995	31.032
1996	30.949
1997	30.629
1998	30.562
1999	30.487
2000	30.463
2001	32.25
2002	34.387
2003	34.486
2004	32.545
2005	32.399
2006	32.365
2007	32.263
2008	31.465
2009	31.359
2010	30.57
2011	30.079
2012	29.349
2013	29.897
2014	29.338
2015	29.98
2016	30.683
2017	30.67
2018	30.6
2019	30.537
2020	30.472
2021	30.4
2022	30.33