Frequencies for psi_90_safety_low_est variable in vwhqi_hosp_ahrq dataset :

PSI_90_SAFE |
 TY_LOW_EST |      Freq.     Percent        Cum.
------------+-----------------------------------
          . |      4,564      100.00      100.00
------------+-----------------------------------
      Total |      4,564      100.00

by Jean Roth , jroth@nber.org , 16 Nov 2016