谢谢，好象有点问题，下面是程序的运行结果，
. do "F:\处理数据文件2.do"

. bysort year newcode: gen id=_n

. keep if id==1
(0 observations deleted)

. drop id

. tab newcode year

           |               year
   newcode |      1992       1993       1994 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      1995       1996       1997 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      1998       1999       2000 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      2001       2002       2003 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      2004       2005       2006 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

. reshape wide  tradesum,i(  year) j( newcode)
newcode contains missing values
r(498);

end of do-file
r(498);

谢谢，好象有点问题，下面是程序的运行结果，
. do "F:\处理数据文件2.do"

. bysort year newcode: gen id=_n

. keep if id==1
(0 observations deleted)

. drop id

. tab newcode year

           |               year
   newcode |      1992       1993       1994 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      1995       1996       1997 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      1998       1999       2000 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      2001       2002       2003 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

           |               year
   newcode |      2004       2005       2006 |     Total
-----------+---------------------------------+----------
        71 |         1          1          1 |        15
        72 |         1          1          1 |        15
        73 |         1          1          1 |        15
        74 |         1          1          1 |        15
        75 |         1          1          1 |        15
        76 |         1          1          1 |        15
        77 |         1          1          1 |        15
        78 |         1          1          1 |        15
        79 |         1          1          1 |        15
-----------+---------------------------------+----------
     Total |         9          9          9 |       135

. reshape wide  tradesum,i(  year) j( newcode)
newcode contains missing values
r(498);

end of do-file
r(498);

preserve
  keep year totaltrad
  duplicates drop
  save ysum.dta, replace
restore

preserve
  drop totaltrad newcode
  duplicates drop
  save ysicsum.dta, replace
restore

* list year sum
  use ysum.dta, clear
  list
 
* list year and sic sum
  use ysicsum.dta, clear
  list