Year	Percent
1990	53.64
1991	52.525
1992	51.408
1993	50.289
1994	49.17
1995	48.484
1996	47.798
1997	47.114
1998	46.43
1999	45.647
2000	44.866
2001	44.088
2002	43.312
2003	42.54
2004	41.43
2005	41.409
2006	41.276
2007	41.223
2008	41.296
2009	41.572
2010	41.68
2011	41.606
2012	41.663
2013	41.655
2014	41.637
2015	41.601
2016	41.533
2017	41.397
2018	41.261
2019	41.125
2020	40.989
2021	40.854
2022	40.718
2023	40.582
2024	40.446
2025	40.311
2026	40.175
2027	40.039
2028	39.903
2029	39.767
2030	39.632