Year	Percent
1990	44.332
1991	44
1992	43.685
1993	43.305
1994	42.948
1995	42.548
1996	42.127
1997	41.847
1998	42.466
1999	42.251
2000	41.868
2001	41.967
2002	41.764
2003	41.528
2004	41.225
2005	41.005
2006	40.764
2007	40.277
2008	40.172
2009	40.461
2010	40.113
2011	39.867
2012	39.602
2013	39.385
2014	39.072
2015	38.824
2016	38.627
2017	38.48
2018	38.333
2019	38.186
2020	38.04
2021	37.893
2022	37.746
2023	37.6
2024	37.453
2025	37.306
2026	37.16
2027	37.013
2028	36.866
2029	36.72
2030	36.573