*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970004004
1970001001
1971002002
1972003003
1973001001
1974001001
1975001001
1976000000
1977001001
1978000000
1979000000
1980000000
1981000000
1982001001
1983000000
1984000000
1985000000
1986000000
1987000000
1988001001
1989000000
1990000000
1991002002
1992003003
1993000000
1994003003
1995002002
1996000000
1997002002
1998004004
1999003003
2000002002
2001004004
2002002002
2003001001
2004000000
2005003003
2006000000
2007000000
2008000000
2009001001
2010000000
2011000000
2012000000
2013000000
2014000000
2015000000
2016000000
2017000000
Total00480048