Year	Percent
1991	20.714
1992	22.207
1993	24.288
1994	25.821
1995	27.165
1996	29.768
1997	28.804
1998	28.37
1999	28.189
2000	28.008
2001	30.912
2002	34.237
2003	38.148
2004	40.45
2005	42.881
2006	42.922
2007	41.946
2008	41.157
2009	40.344
2010	39.84
2011	38.498
2012	38.247
2013	38.27
2014	40.577
2015	43.094
2016	44.445
2017	46.417
2018	47.646
2019	48.754
2020	49.791
2021	50.802
2022	51.631