Year	Number
1971	13.68358
1976	17.59576
1977	17.03502
2000	23.32554
2001	25.88722
2002	24.85211
2003	25.38297
2004	26.26465
2005	28.71445
2006	30.65093
2007	22.02082
2009	22.60539
2011	23.70344
2012	22.91459
2013	22.79344
2014	21.65028
2015	19.21098
2016	18.57893
2017	20.08785
2018	28.24773