I am using -import dbase- to convert a DBF file to DTA. However, it is replacing some of the non-missing cells to missing values.
When I manually convert the same file with Stat/Transfer I get no missing values.

Code:
. import dbase using dn99, clear case(lower)
(21 vars, 3,256,433 obs)

. save SINASC_import_dbase, replace
file SINASC_import_dbase.dta saved

. codebook dtnasc

--------------------------------------------------------------------------------------------------------------------------------------------
dtnasc                                                                                                                                DTNASC
--------------------------------------------------------------------------------------------------------------------------------------------

                  type:  string (str8)

         unique values:  366                      missing "":  994,858/3,256,433

              examples:  ""
                         "05031999"
                         "13111999"
                         "22081999"

.
. use SINASC_stat_transfer, clear

. codebook dtnasc

--------------------------------------------------------------------------------------------------------------------------------------------
dtnasc                                                                                                                           (unlabeled)
--------------------------------------------------------------------------------------------------------------------------------------------

                  type:  string (str8)

         unique values:  366                      missing "":  0/3,256,433

              examples:  "06111999"
                         "12121999"
                         "19021999"
                         "25031999"

.
end of do-file
Does anyone know why would the command -import dbase- transform some non-missing values in missing values and how I can prevent this from happening?

Many thanks
Paula