Year	Percent
1991	16.909
1992	16.998
1993	17.152
1994	17.304
1995	17.464
1996	17.553
1997	17.699
1998	17.89
1999	18.089
2000	18.309
2001	18.166
2002	18.07
2003	18.037
2004	18.118
2005	18.385
2006	18.733
2007	19.087
2008	19.39
2009	19.695
2010	19.959
2011	20.103
2012	20.231
2013	20.285
2014	20.337
2015	20.434
2016	20.621
2017	20.753
2018	20.864
2019	20.959
2020	21.04
2021	21.099
2022	21.144