Year	Percent
1990	39.923
1991	40.022
1992	39.844
1993	39.779
1994	39.624
1995	39.545
1996	39.376
1997	39.147
1998	38.913
1999	38.684
2000	38.465
2001	38.4
2002	38.347
2003	38.289
2004	38.202
2005	38.078
2006	37.851
2007	37.603
2008	38.055
2009	38.519
2010	39.012
2011	39.524
2012	40.047
2013	40.568
2014	41.07
2015	40.921
2016	40.819
2017	40.77
2018	40.694
2019	40.586
2020	40.447
2021	40.311
2022	40.146
2023	39.967
2024	39.795
2025	39.647
2026	39.552
2027	39.482
2028	39.43
2029	39.388
2030	39.351