Year	Percent
1991	19.17
1992	19.344
1993	18.757
1994	19.694
1995	18.554
1996	18.295
1997	17.398
1998	15.529
1999	16.855
2000	16.707
2001	17.193
2002	17.824
2003	21.897
2004	19.537
2005	21.29
2006	22.633
2007	23.019
2008	20.754
2009	20.617
2010	19.53
2011	19.22
2012	21.352
2013	17.12
2014	17.105
2015	17.57
2016	18.183
2017	18.96
2018	19.176
2019	19.443
2020	19.618
2021	19.736
2022	19.728