How many bilateral relationships share a regional trade agreement in the
sample?
Time period: 1958-2015. 2,296,858 observations => 39,601 observations per year
. table year if iso_o!=iso_d, c(sum rta)
----------------------
year | sum(rta)
----------+-----------
1958 | 42
1959 | 62
1960 | 104
1961 | 124
1962 | 124
1963 | 136
1964 | 136
1965 | 136
1966 | 156
1967 | 156
1968 | 156
1969 | 156
1970 | 170
1971 | 170
1972 | 170
1973 | 312
1974 | 384
1975 | 424
1976 | 424
1977 | 426
1978 | 446
1979 | 446
1980 | 446
1981 | 468
1982 | 468
1983 | 470
1984 | 480
1985 | 480
1986 | 568
1987 | 568
1988 | 568
1989 | 570
1990 | 570
1991 | 582
1992 | 662
1993 | 772
1994 | 1066
1995 | 1538
1996 | 1636
1997 | 1660
1998 | 2126
1999 | 2220
2000 | 2334
2001 | 2532
2002 | 2636
2003 | 2896
2004 | 3444
2005 | 3528
2006 | 3620
2007 | 3754
2008 | 3872
2009 | 4832
2010 | 5146
2011 | 5166
2012 | 5258
2013 | 5576
2014 | 6006
2015 | 6010
----------------------