Year	Percent
1990	52.036
1991	49.765
1992	51.498
1993	52.591
1994	48.864
1995	52.012
1996	47.491
1997	48.796
1998	46.278
1999	46.342
2000	46.015
2001	43.397
2002	42.513
2003	40.455
2004	38.895
2005	37.968
2006	35.394
2007	34.43
2008	32.598
2009	31.449
2010	30.504
2011	29.1
2012	28.7
2013	27.615
2014	27.219
2015	26.153
2016	26.11
2017	25.855
2018	25.601
2019	25.347
2020	25.092
2021	24.838
2022	24.584
2023	24.329
2024	24.075
2025	23.821
2026	23.566
2027	23.312
2028	23.058
2029	22.803
2030	22.549