Year	Percent
1991	41.048
1992	41.786
1993	40.57
1994	40.157
1995	39.855
1996	39.502
1997	39.339
1998	39.301
1999	39.189
2000	38.837
2001	38.773
2002	38.803
2003	38.868
2004	37.957
2005	39.505
2006	39.368
2007	38.283
2008	37.825
2009	37.274
2010	36.758
2011	37.487
2012	38.001
2013	38.004
2014	38.302
2015	38.241
2016	37.082
2017	36.613
2018	36.528
2019	36.443
2020	36.361
2021	36.269
2022	36.183