Year	Percent
1990	52.512
1991	51.728
1992	49.751
1993	49.847
1994	49.758
1995	49.109
1996	48.664
1997	47.46
1998	43.529
1999	39.677
2000	35.949
2001	32.384
2002	29.011
2003	25.856
2004	22.933
2005	22.525
2006	22.121
2007	21.723
2008	21.33
2009	21.162
2010	20.259
2011	19.162
2012	16.733
2013	16.044
2014	16.82
2015	16.876
2016	15.295
2017	15.031
2018	14.767
2019	14.503
2020	14.239
2021	13.975
2022	13.711
2023	13.447
2024	13.183
2025	12.919
2026	12.655
2027	12.391
2028	12.127
2029	11.863
2030	11.599