15.5
2018
5
10
15
20
25
30
21.9
1990
23.8
1991
23.4
1992
22.9
1993
23.4
1994
23.8
1995
22.7
1996
22.4
1997
23.0
1998
22.6
1999
21.4
2000
21.7
2001
20.3
2002
20.7
2003
20.2
2004
19.4
2005
19.7
2006
20.3
2007
19.7
2008
19.2
2009
19.3
2010
20.2
2011
15.0
2012
12.7
2013
15.2
2014
14.2
2015
14.3
2016
15.3
2017
15.5
2018
