John Mullahy, "Heterogeneity, Excess Zeros, and the Structure of Count
Data Models", Journal of Applied Econometrics, Vol. 12, No. 3, 1997,
pp. 337-350.

The data are in column-separated, multiple-lines-per-record, ASCII 
format, arrayed as follows:

   1. SEX         byte                                                   
   2. AGE         float                                                  
   3. INCOME      float                                                  
   4. ILLNESS     byte                                                   
   5. ACTDAYS     byte                                                   
   6. HSCORE      byte                                                   
   7. DOCTORCON   byte                                                   
   8. LEVYPLUS    byte                                                   
   9. FREEPOOR    byte                                                   
  10. FREEREPAT   byte                                                   
  11. CHCOND1     byte                                                   
  12. CHCOND2     byte                                                   
  13. AGESQ       float                  

The dependent variable is the number of doctor visits (consultations)
during the recall period (DOCTORCON).  The covariates are SEX, AGE, AGE
SQUARED (AGESQ), INCOME, three insurance status measures (LEVYPLUS,
FREEPOOR, and FREEREPAT), ILLNESS (recent illness), ACTDAYS (number of
reduced activity days), HSCORE (general health questionnaire score), two
measures of chronic conditions (CHCOND1 and CHCOND2). 

The sample consists of 5,190 observations and is from the 1977-78
Australian Health Survey and contains information on health service
utilization and covariates describing factors that affect health care
utilization propensities.  The sample, whose distribution in entirety is
limited by agreement with its Australian source, were kindly provided to
me by Prof. P.K. Trivedi.  The dataset posted here contains only those
variables used in the analysis.  A detailed description is provided in: 

 Cameron, A.C. and P.K. Trivedi. 1986. "Econometric Models Based on 
 Count Data: Comparisons and Applications of Some Estimators and 
 Tests." Journal of Applied Econometrics 1: 29-53.

The interested analyst might also wish to consult the dataset and
associated description pertaining to the paper by Cameron and Johansson in
the same issue of the JAE. 

The data file mullahy.dat, which is in DOS format, is zipped into a ZIP
archive jm-data.zip.  The zipped size of the dataset is approximately 28k;
unzipped it is about 740k.