Year	Number
1991	14.78189
1992	13.61197
1999	16.96926
2000	17.96735
2001	20.07522
2002	19.87221
2003	19.47104
2004	19.31256
2005	13.26204
2006	12.17326
2007	12.35549
2008	12.45304
2009	12.61564
2010	12.53013
2011	12.05147
2012	11.4286
2013	11.40112
2014	11.23999
2015	10.71371
2016	10.66598
2017	11.74621
2018	11.93428