Year	Percent
1990	39.159
1991	39.222
1992	39.226
1993	39.192
1994	39.177
1995	39.248
1996	39.294
1997	39.331
1998	39.373
1999	39.399
2000	39.387
2001	39.412
2002	39.387
2003	39.323
2004	39.243
2005	39.168
2006	39.121
2007	39.066
2008	39
2009	38.913
2010	38.796
2011	38.731
2012	38.642
2013	38.533
2014	38.417
2015	38.296
2016	38.215
2017	38.152
2018	38.09
2019	38.027
2020	37.965
2021	37.902
2022	37.839
2023	37.777
2024	37.714
2025	37.651
2026	37.589
2027	37.526
2028	37.463
2029	37.401
2030	37.338