Frequencies for first 10,000 rows of totamb variable in nhamcsopd2000 dataset :

     total # of ambulatory surgical |
                         procedures |      Freq.     Percent        Cum.
------------------------------------+-----------------------------------
                                  0 |      9,240       92.40       92.40
                                  1 |        445        4.45       96.85
                                  2 |         48        0.48       97.33
All fields blank including None box |        267        2.67      100.00
------------------------------------+-----------------------------------
                              Total |     10,000      100.00

by Jean Roth , jroth@nber.org , 28 Mar 2016