Year	Percent
1991	32.978
1992	33.625
1993	31.176
1994	28.97
1995	29.221
1996	25.759
1997	27.051
1998	27.471
1999	27.974
2000	27.264
2001	28.846
2002	28.807
2003	27.983
2004	28.526
2005	28.839
2006	28.019
2007	28.486
2008	28.631
2009	26.82
2010	24.071
2011	23.907
2012	25.088
2013	23.834
2014	23.214
2015	22.741
2016	22.368
2017	21.457
2018	21.117
2019	20.822
2020	20.529
2021	20.242
2022	19.947