Year	Percent
1991	39.919
1992	39.124
1993	38.703
1994	38.971
1995	39.646
1996	39.275
1997	38.249
1998	32.623
1999	32.551
2000	34.069
2001	34.934
2002	35.931
2003	35.528
2004	36.257
2005	36.028
2006	33.277
2007	31.303
2008	28.702
2009	26.845
2010	26.921
2011	26.99
2012	27.833
2013	27.602
2014	29.601
2015	30.932
2016	31.183
2017	31.492
2018	31.431
2019	31.35
2020	31.12
2021	30.716
2022	30.119