Year	Percent
1991	32.338
1992	32.71
1993	34.085
1994	34.471
1995	35.654
1996	37.01
1997	37.536
1998	38.129
1999	38.281
2000	38.941
2001	39.059
2002	38.946
2003	38.791
2004	38.537
2005	38.258
2006	37.37
2007	36.884
2008	35.806
2009	35.527
2010	35.883
2011	35.573
2012	35.14
2013	34.128
2014	33.375
2015	32.053
2016	32.186
2017	31.989
2018	31.206
2019	30.349
2020	29.603
2021	28.911
2022	28.231