Year	Percent
1991	45.459
1992	33.014
1993	29.374
1994	29.015
1995	31.611
1996	35.721
1997	38.41
1998	39.287
1999	35.847
2000	37.837
2001	34.86
2002	35.085
2003	34.792
2004	35.058
2005	34.511
2006	32.906
2007	33.108
2008	35.049
2009	35.676
2010	36.344
2011	36.639
2012	37.583
2013	38.498
2014	38.961
2015	39.403
2016	39.501
2017	39.786
2018	40.604
2019	41.285
2020	42.185
2021	42.927
2022	43.566