Year	Percent
1991	14.321
1992	14.51
1993	14.978
1994	13.624
1995	15.135
1996	15.527
1997	15.473
1998	14.657
1999	14.84
2000	14.882
2001	14.896
2002	15.618
2003	15.662
2004	14.984
2005	14.846
2006	16.87
2007	17.062
2008	16.891
2009	17.033
2010	17.024
2011	16.83
2012	16.745
2013	17.071
2014	17.711
2015	18.467
2016	18.67
2017	18.954
2018	19.343
2019	19.626
2020	19.937
2021	20.283
2022	20.616