Year	Percent
1991	18.432
1992	19.206
1993	20.005
1994	20.803
1995	21.553
1996	22.906
1997	24.229
1998	25.564
1999	26.995
2000	28.606
2001	30.822
2002	33.238
2003	35.86
2004	38.285
2005	40.661
2006	43.556
2007	42.793
2008	42.212
2009	41.311
2010	40.902
2011	40.268
2012	39.424
2013	38.824
2014	37.855
2015	34.527
2016	31.538
2017	31.957
2018	32.306
2019	32.594
2020	32.844
2021	33.07
2022	33.292