*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970000000
1970000000
1971000000
1972000000
1973000000
1974000000
1975000000
1976000000
1977000000
1978000000
1979000000
1980000000
1981000000
1982000000
1983000000
1984000000
1985000000
1986000000
1987000000
1988000011
1989000000
1990000044
1991000000
1992000000
1993000000
1994000112
1995000000
1996000022
1997000000
1998002002
1999002316
2000000033
2001000033
2002000000
2003000000
2004000000
2005000000
2006000000
2007000000
2008000000
2009000011
2010000000
2011000000
2012000000
2013000101
2014000000
2015000000
2016000000
2017000000
2018000000
Total00451625