Year	Percent
1991	30.751
1992	31.99
1993	33.858
1994	36.3
1995	37.11
1996	34.971
1997	33.136
1998	30.376
1999	29.344
2000	28.74
2001	28.515
2002	29.625
2003	29.836
2004	32.254
2005	31.034
2006	31.039
2007	31.368
2008	31.453
2009	30.971
2010	29.436
2011	30.69
2012	29.411
2013	28.437
2014	25.175
2015	24.673
2016	24.642
2017	24.217
2018	23.976
2019	23.613
2020	23.098
2021	22.468
2022	21.723