Year	Percent
1991	68.0346
1992	68.11997
1993	68.30954
1994	68.23464
1995	68.11248
1996	67.91639
1997	67.6435
1998	67.30227
1999	66.90625
2000	66.47175
2001	65.88601
2002	64.99466
2003	64.04251
2004	62.93845
2005	62.02828
2006	60.9746
2007	59.82741
2008	58.24874
2009	56.65887
2010	55.00315
2011	53.23568
2012	51.39596
2013	49.47972
2014	47.61313
2015	46.57673
2016	45.70598
2017	44.91202
2018	44.16818
2019	43.49685