_dta:
  1.  gaz2016zcta5centroid set up by Jean Roth , jroth@nber.org , 15 Jun 2017
  2.  Source Page:
  3.  Data source : http://www2.census.gov/geo/docs/maps-data/data/gazetteer/2016_Gazetteer/2016_Gaz_zcta_national.zip
  4.  Source: 2016_Gaz_zcta_national.txt
  5.  ------------------------------------------------
  6.  from http://www.census.gov/prod/cen2010/doc/sf1.pdf :
  7.  ------------------------------------------------
  8.  Internal point-
  9.  The Census Bureau calculates an internal point (latitude and longitude
 10.  coordinates) for each geographic entity. For many geographic entities,
 11.  the internal point is at or near the geographic center of the entity.
 12.  For some irregularly shaped entities (such as those shaped like a
 13.  crescent), the calculated geographic center may be located outside
 14.  the boundaries of the entity. In such instances, the internal point
 15.  is identified as a point inside the entity boundaries nearest to the
 16.  calculated geographic center and, if possible, within a land polygon.
 17.  ------------------------------------------------
 18.  by Jean Roth , jroth@nber.org , 15 Jun 2017
 19.  Census Gazetteer ZCTA5 file
 20.  Unique identifier is zcta5
 21.  Distances between ZCTA5 that are within 100 miles

  obs:    19,051,920                          
 vars:             3                          15 Jun 2017 17:01
 size:   342,934,560                          (_dta has notes)
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              storage   display    value
variable name   type    format     label      variable label
---------------------------------------------------------------------------------------------------------------------------------------------------------------
zip1            str5    %9s                   Five digit ZIP Code Tabulation Area Census Code
zip2            str5    %9s                   Five digit ZIP Code Tabulation Area Census Code
mi_to_zcta5     double  %10.0g                Distance between ZCTAs that are within 100 miles
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Sorted by: zip1  mi_to_zcta5  zip2