Year	Percent
1991	30.98
1992	29.659
1993	29.602
1994	29.376
1995	29.605
1996	29.279
1997	29.562
1998	29.9
1999	30.908
2000	32.075
2001	30.689
2002	31.032
2003	31.989
2004	28.639
2005	28.513
2006	30.064
2007	31.964
2008	28.571
2009	27.579
2010	28.174
2011	29.047
2012	28.295
2013	28.573
2014	28.684
2015	28.537
2016	28.426
2017	28.428
2018	28.424
2019	28.42
2020	28.417
2021	28.414
2022	28.41