Year	Percent
1991	62.03144
1992	56.25573
1993	53.42845
1994	58.5143
1995	61.03115
1996	72.54639
1997	85.29255
1998	99.87602
1999	107.88474
2000	127.59079
2001	119.00895
2002	106.72702
2003	106.53699
2004	111.56801
2005	114.55582
2006	133.15188
2007	136.54916
2008	137.62429
2009	123.1058
2010	140.28167
2011	152.54172
2012	155.44408
2013	153.54333
2014	153.82835
2015	155.11568
2016	155.63357
2017	158.77805