When should I use household weighting rather than population weighting?

Household weighting vs population weighting

Most of the time TGI data is analysed using a population weighting. This is because consumption questions usually refer to the individual (e.g. Which brands do you drink?). However, with regard to white goods and other durables it may be more appropriate to use a household weighting. To find out how many washing machines are owned, for example, it would be necessary to weight by household to avoid overstating the figure. On the other hand, to find out how many adults have a washing machine the population weighting should be used. It should be remembered that household weighting can only be used for questions asked of all adults.

It is particularly important to use a household weighting when looking at spend on appliances such as washing machines. A couple might spend £200 on a washing machine (£100 each). If both subsequently filled in a TGI questionnaire, a population weighting would count their expenditure twice for a total spend of £400.

The following table shows household and population figures for freezer ownership. We can see two very different results. 1,532,000 people have a freezer at home. However, most of these appliances will be shared. Therefore the household figure is lower, telling us that 711,000 households have at least one freezer.

Feezer ownership………………………Population……………………….Household

(000s)…………………………………….. 1,532,000……………………………..711

% population/households………………..44%………………………………..40%