What domain would be the most appropriate set to use for a function that predicts the number of household online-devices in?

The arguments for the function could be one or more of the total number of households, the number of people in each household, their disposable income, ages, where in the world they lived. There are many other possible factors. So the domain would be a multi-dimensional space in which some variables were qualitative (where they lived), and some quantitative.