Year	Percent
1991	74.952
1992	74.878
1993	74.971
1994	75.037
1995	74.985
1996	75.042
1997	75.074
1998	75.099
1999	75.216
2000	75.215
2001	75.524
2002	74.954
2003	73.907
2004	72.954
2005	72.332
2006	71.876
2007	71.629
2008	71.593
2009	70.972
2010	70.66
2011	69.646
2012	69.598
2013	69.668
2014	69.634
2015	69.534
2016	69.706
2017	69.186
2018	68.767
2019	68.375
2020	68.074
2021	67.8
2022	67.571