Year	Percent
1990	38.486
1991	33.237
1992	28.373
1993	34.91
1994	30.294
1995	31.668
1996	28.669
1997	29.211
1998	28.032
1999	33.097
2000	30.145
2001	30.355
2002	30.566
2003	30.778
2004	30.99
2005	31.204
2006	31.418
2007	31.633
2008	31.848
2009	32.065
2010	32.282
2011	32.5
2012	35.5
2013	36
2014	34.49
2015	37.032
2016	39.427
2017	39.515
2018	39.604
2019	39.693
2020	39.782
2021	39.871
2022	39.96
2023	40.049
2024	40.138
2025	40.227
2026	40.316
2027	40.405
2028	40.494
2029	40.583
2030	40.672