Year	Years
1986	11.2
1987	11.8
1988	12.4
1989	13.1
1990	13.8
1991	14.6
1992	15.4
1993	16.2
1994	17.1
1995	18
1996	19
1997	19.9
1998	21
1999	22.1
2000	23.2
2001	24.5
2002	25.7
2003	26.8
2004	27.6
2005	28
2006	28
2007	27.9
2008	27.6
2009	27.1
2010	26.5
2011	26
2012	25.2
2013	24.5