Year	Percent
1990	14.89189
1991	14.96056
1992	15.02882
1993	15.09348
1994	15.19375
1995	15.58509
1996	15.77652
1997	15.99869
1998	16.24037
1999	16.48285
2000	16.72211
2001	16.93931
2002	17.11994
2003	17.2434
2004	17.37143
2005	17.51191
2006	17.67005
2007	17.83179
2008	17.9988
2009	18.16262
2010	18.32824
2011	18.56718
2012	18.74889
2013	18.93127
2014	19.11227
2015	19.29989
2016	19.49499
2017	19.68978