Year	Percent
1991	32.861
1992	31.93
1993	31.295
1994	29.081
1995	35.098
1996	43.178
1997	38.76
1998	41.015
1999	41.073
2000	41.817
2001	40.23
2002	39.469
2003	37.82
2004	38.66
2005	38.855
2006	38.469
2007	39.065
2008	37.215
2009	34.681
2010	34.706
2011	34.435
2012	29.238
2013	28.713
2014	26.735
2015	26.423
2016	31.072
2017	30.692
2018	30.526
2019	30.267
2020	30.053
2021	29.993
2022	29.959