Year	Percent
1990	21.341
1991	21.351
1992	21.409
1993	21.517
1994	22.329
1995	21.004
1996	20.261
1997	19.537
1998	18.833
1999	19.839
2000	19.901
2001	20.081
2002	18.839
2003	19.258
2004	19.723
2005	20.233
2006	20.787
2007	22.745
2008	22.799
2009	22.864
2010	22.78
2011	21.924
2012	22.114
2013	22.839
2014	22.529
2015	22.22
2016	22.043
2017	22.183
2018	22.315
2019	22.448
2020	22.589
2021	22.738
2022	22.898
2023	23.057
2024	23.201
2025	23.32
2026	23.421
2027	23.499
2028	23.575
2029	23.676
2030	23.821