Frequencies for first 10,000 rows of cntrspop variable in natl1990 dataset :

 Population |
    Size of |
  County of |
  Residence |      Freq.     Percent        Cum.
------------+-----------------------------------
          1 |      1,691       16.91       16.91
          2 |        350        3.50       20.41
          3 |      2,389       23.89       44.30
          9 |      5,568       55.68       99.98
          Z |          2        0.02      100.00
------------+-----------------------------------
      Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 3 Jan 2016