Year	Percent
1990	42.348
1991	42.97
1992	43.376
1993	43.299
1994	43.741
1995	43.234
1996	42.92
1997	43.178
1998	43.212
1999	43.172
2000	42.626
2001	42.141
2002	41.891
2003	41.579
2004	41.193
2005	40.795
2006	40.638
2007	40.035
2008	39.933
2009	40.427
2010	40.378
2011	39.793
2012	39.743
2013	39.926
2014	39.783
2015	39.585
2016	38.98
2017	38.87
2018	38.745
2019	38.583
2020	38.379
2021	38.197
2022	37.979
2023	37.742
2024	37.524
2025	37.342
2026	37.255
2027	37.206
2028	37.175
2029	37.144
2030	37.104