Year	Percent
1990	21.256
1991	21.62
1992	21.915
1993	22.112
1994	22.27
1995	22.482
1996	22.71
1997	23.163
1998	23.678
1999	24.185
2000	24.725
2001	25.037
2002	25.31
2003	25.588
2004	25.938
2005	26.32
2006	27.235
2007	28.091
2008	28.896
2009	29.549
2010	30.043
2011	30.441
2012	30.942
2013	31.3
2014	31.576
2015	31.868
2016	31.728
2017	31.663
2018	31.57
2019	31.47
2020	31.37
2021	31.139
2022	30.921
2023	30.722
2024	30.538
2025	30.359
2026	30.08
2027	29.814
2028	29.586
2029	29.424
2030	29.341