Year	Percent
1990	37.335
1991	36.92
1992	36.42
1993	35.92
1994	34.066
1995	32.26
1996	30.506
1997	28.806
1998	27.164
1999	25.582
2000	24.061
2001	22.604
2002	21.21
2003	21.247
2004	21.117
2005	21.197
2006	21.006
2007	20.751
2008	20.687
2009	20.574
2010	20.422
2011	20.231
2012	20.064
2013	19.883
2014	19.755
2015	19.659
2016	19.559
2017	19.386
2018	19.213
2019	19.04
2020	18.867
2021	18.694
2022	18.52
2023	18.347
2024	18.174
2025	18.001
2026	17.828
2027	17.655
2028	17.481
2029	17.308
2030	17.135