Variables contained in the default data file fluid.gdx (or fluid.txt) include the following:

y:         	  Quantity of fluid milk purchased. Name changed to "y" in data file;
cons:      	  A column of scalar "1" to capture the intercept term;
city:      	  1 if Household is located in a town with> 15,000 population;
sm_city:          1 if Household is located in a town with 2,500-15,000 population;
num_yung:         Number of household members;
incomet:          Quarterly household income (10,000 Pesos);
num_yung_incomet: Multiplication of quarterly income and number of members;
perfafh: 	  Percent of weekly household food expenditures spent on food purchased and consumed outside the home;
refrig: 	  1 if the household own a refrigerator/freezer.