_dta:
  1.  zipcode1990 set up by Jean Roth , jroth@nber.org , 30 Mar 2016
  2.  Source Page: http://www.census.gov/geo/maps-data/data/gazetteer1990.html
  3.  Source File URL: http://www2.census.gov/geo/docs/maps-data/data/gazetteer/zips.zip
  4.  Source File: zipcode.csv
  5.  by Jean Roth , jroth@nber.org , 1 Apr 2016
  6.  Census Gazetteer Zipcode file
  7.  Unique identifier is zipcode
  8.  Distances between Zipcode that are within 500 miles

  obs:   218,759,050                          
 vars:             6                          1 Apr 2016 18:13
 size: 8,312,843,900                          (_dta has notes)
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              storage   display    value
variable name   type    format     label      variable label
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fipsst1         str2    %9s                   FIPS State Code
zipcode1        str5    %9s                   ZIP Code
mi_to_zipcode   double  %10.0g                Distance between ZIP Codes that are within 500 miles
fipsst2         str2    %9s                   FIPS State Code
zipcode2        str5    %9s                   ZIP Code
name            str16   %16s                  ZIP Code Name
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Sorted by: fipsst1  zipcode1  mi_to_zipcode  fipsst2  zipcode2