Year	Percent
1991	51.564
1992	49.909
1993	49.108
1994	48.346
1995	47.501
1996	47.019
1997	46.491
1998	46.082
1999	45.613
2000	45.315
2001	44.515
2002	44.179
2003	43.12
2004	42.881
2005	41.076
2006	40.852
2007	41.372
2008	41.168
2009	40.767
2010	40.186
2011	40.191
2012	40.142
2013	39.632
2014	40.059
2015	39.713
2016	39.232
2017	39.131
2018	38.904
2019	38.66
2020	38.502
2021	38.315
2022	38.148