_dta:
  1.  by Jean Roth , jroth@nber.org , 2012-10-10
  2.  by Jean Roth , jroth@nber.org , 11 Aug 2014
  3.  Census 2000 SF1 Summary Level 050
  4.  Unique identifier is county
  5.  Distances between County that are within 500 miles

  obs:     2,640,284                          
 vars:             3                          11 Aug 2014 10:15
 size:    47,525,112                          (_dta has notes)
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              storage   display    value
variable name   type    format     label      variable label
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county1         str5    %9s                   County
mi_to_county    double  %10.0g                Distance between counties that are within 500 miles
county2         str5    %9s                   County
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Sorted by: county1  mi_to_county  county2