Year	Percent
1990	18.659
1991	18.783
1992	19.022
1993	19.3
1994	19.785
1995	20.19
1996	20.195
1997	20.199
1998	20.204
1999	20.209
2000	20.213
2001	20.218
2002	20.223
2003	20.227
2004	20.232
2005	20.237
2006	20.241
2007	20.246
2008	20.251
2009	20.255
2010	20.26
2011	20.605
2012	20.94
2013	21.287
2014	21.575
2015	21.845
2016	22.103
2017	22.137
2018	22.171
2019	22.205
2020	22.239
2021	22.273
2022	22.307
2023	22.342
2024	22.376
2025	22.41
2026	22.444
2027	22.478
2028	22.512
2029	22.546
2030	22.58