Year	Percent
1991	22.54
1992	22.472
1993	23.239
1994	23.434
1995	22.273
1996	20.858
1997	21.503
1998	19.362
1999	20.033
2000	19.461
2001	19.498
2002	16.99
2003	16.978
2004	15.278
2005	16.12
2006	15.098
2007	14.962
2008	15.19
2009	14.486
2010	14.729
2011	15.775
2012	15.573
2013	15.347
2014	14.99
2015	14.7
2016	14.706
2017	14.662
2018	14.59
2019	14.557
2020	14.551
2021	14.541
2022	14.529