Year	Percent
1991	27.73
1992	28.138
1993	27.466
1994	27.389
1995	27.863
1996	28.199
1997	28.748
1998	29.722
1999	30.958
2000	30.289
2001	30.385
2002	30.857
2003	30.92
2004	30.641
2005	31.229
2006	34.604
2007	35.455
2008	35.788
2009	36.339
2010	37.07
2011	37.394
2012	35.692
2013	34.104
2014	34.235
2015	36.277
2016	37.43
2017	37.838
2018	38.169
2019	39.309
2020	40.186
2021	40.872
2022	41.576