*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970000000
1970000000
1971000000
1972000000
1973001001
1974000000
1975000000
1976001001
1977000000
1978001001
1979000000
1980000000
1981000000
1982000000
1983000000
1984000000
1985000000
1986000000
1987000000
1988001001
1989000000
1990000000
1991000000
1992000000
1993000000
1994000000
1995001001
1996000000
1997000000
1998000000
1999001001
2000001001
2001001001
2002000000
2003000000
2004000000
2005001001
2006001001
2007000000
2008001001
2009001001
2010003003
2011003003
2012002002
2013001001
2014000000
2015001001
2016000000
2017000000
Total00220022