We tested the sensitivity of the total number of hours spent in household production to the inclusion of secondary activity and imputed care hours:

• using only primary and secondary hours reduces total hours by 39 per cent in 2000;
• using only primary hours reduces total hours by 50 per cent in 2000;
• using 50 per cent of time spent in primary activities and 50 per cent of time spent in secondary activities, where there are two activities going on at the same time, reduces total hours by 50 per cent in 2000.