Year	Percent
1990	34.121
1991	35.93
1992	38.105
1993	36.944
1994	37.706
1995	35.283
1996	36.364
1997	37.394
1998	37.708
1999	39.708
2000	41.382
2001	41.142
2002	42.381
2003	42.525
2004	44.345
2005	45.368
2006	46.716
2007	46.819
2008	46.954
2009	48.767
2010	48.828
2011	49.408
2012	50.97
2013	51.109
2014	51.992
2015	53.559
2016	52.24
2017	52.269
2018	52.314
2019	52.372
2020	52.442
2021	52.435
2022	52.446
2023	52.474
2024	52.512
2025	52.554
2026	52.513
2027	52.472
2028	52.436
2029	52.403
2030	52.375