Year	Percent
1991	14.891
1992	15.687
1993	16.281
1994	17.05
1995	17.642
1996	18.014
1997	20.582
1998	22.131
1999	21.431
2000	21.085
2001	20.453
2002	21.463
2003	22.585
2004	23.32
2005	24.746
2006	26.114
2007	26.322
2008	26.613
2009	27.024
2010	27.612
2011	28.279
2012	28.984
2013	29.897
2014	30.201
2015	30.687
2016	31.174
2017	31.706
2018	32.508
2019	33.395
2020	34.243
2021	35.072
2022	35.769