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      I recently shifted our USGS topographic set to
      accommodate superceding additions.  The shift
      was made by measuring random groups of 100 maps
      with calipers, applying the average to the space
      available, and calipering the hundred map average
      as the shift proceded.  The method worked well
      and about 90,000 maps were moved quickly and evenly
      distributed.  The tolerance of our 'average' left
      about 2.25 extra inches at the end of the shift.
 
      I am now concerned with future growth. Is it
      appropriate to anticipate an even distribution
      in the creation of superceding topos by USGS?
      Or, should one expect that some individual states/
      locals will be more quickly superceded than others?
 
      Thanks! R.Balliot