Year	Percent
1990	18.173
1991	18.174
1992	18.176
1993	18.177
1994	18.182
1995	18.185
1996	18.186
1997	18.19
1998	18.19
1999	18.189
2000	18.189
2001	18.189
2002	18.189
2003	18.188
2004	18.187
2005	18.187
2006	18.187
2007	18.189
2008	18.192
2009	18.194
2010	18.196
2011	18.2
2012	18.203
2013	18.205
2014	18.209
2015	18.212
2016	18.215
2017	18.216
2018	18.217
2019	18.218
2020	18.219
2021	18.22
2022	18.221
2023	18.221
2024	18.222
2025	18.223
2026	18.224
2027	18.225
2028	18.226
2029	18.227
2030	18.228