Year	Percent
1991	39.109
1992	38.838
1993	39.483
1994	39.341
1995	40.134
1996	39.502
1997	38.727
1998	37.158
1999	37.174
2000	37.108
2001	38.079
2002	39.234
2003	38.386
2004	40.24
2005	41.254
2006	40.762
2007	41.301
2008	41.773
2009	40.197
2010	40.158
2011	39.404
2012	39.049
2013	38.354
2014	38.052
2015	35.843
2016	32.995
2017	31.351
2018	32.906
2019	33.414
2020	33.358
2021	33.267
2022	33.146