Year	Percent
1990	39.561
1991	39.5
1992	39.2
1993	38.746
1994	38.304
1995	38.038
1996	37.762
1997	37.711
1998	37.645
1999	37.538
2000	37.491
2001	37.334
2002	37.111
2003	36.571
2004	36.289
2005	35.883
2006	35.387
2007	35.312
2008	34.938
2009	34.947
2010	34.66
2011	34.416
2012	34.28
2013	34.023
2014	33.631
2015	33.323
2016	32.987
2017	32.814
2018	32.64
2019	32.467
2020	32.294
2021	32.12
2022	31.947
2023	31.774
2024	31.6
2025	31.427
2026	31.254
2027	31.08
2028	30.907
2029	30.734
2030	30.56