Year	Number
1996	19.60302
1997	18.94936
1998	19.88625
1999	19.20884
2000	18.77265
2001	18.27197
2002	17.93677
2003	17.72563
2005	17.52572
2006	17.06071
2007	16.69378
2008	16.02884
2009	14.78459
2010	14.25609
2011	13.83132
2012	13.67519
2013	13.71278
2014	13.69721
2015	13.702
2016	13.50611