Year	Percent
1991	21.548
1992	20.861
1993	19.995
1994	19.745
1995	20.187
1996	21.011
1997	21.172
1998	21.567
1999	21.67
2000	22.306
2001	23.082
2002	23.328
2003	23.682
2004	24.306
2005	24.218
2006	24.141
2007	24.456
2008	24.62
2009	24.248
2010	24.603
2011	25.104
2012	25.506
2013	26.195
2014	26.834
2015	27.427
2016	27.639
2017	27.656
2018	28.074
2019	28.563
2020	29.06
2021	29.562
2022	30.043