*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970100001
1970000000
1971000000
1972100001
1973000000
1974000000
1975100001
1976200002
1977000000
1978100001
1979100102
1980100001
1981200204
1982000000
1983100001
1984000000
1985100001
1986100001
1987000000
1988000101
1989100001
1990300003
1991000101
1992100001
1993200002
1994200204
1995300205
1996100102
1997200406
1998200305
1999100102
2000200204
2001100203
2002200406
2003100102
2004200002
2005100102
2006000404
2007100304
2008300205
2009100405
2010100203
2011200608
2012100102
2013000011
2014000000
2015000202
2016000101
2017000000
2018000000
Total4900531103