Year	Percent
1991	28.662
1992	28.653
1993	28.681
1994	28.71
1995	28.762
1996	28.793
1997	28.642
1998	28.79
1999	28.968
2000	29.177
2001	29.309
2002	29.446
2003	29.601
2004	29.751
2005	29.905
2006	30.179
2007	27.911
2008	28.212
2009	28.504
2010	28.82
2011	29.188
2012	29.581
2013	29.993
2014	30.388
2015	30.757
2016	30.96
2017	31.125
2018	31.296
2019	31.42
2020	31.545
2021	31.67
2022	31.787