Table 4.

Details on the challenges, direction on caregiving hours and methods to address each issue

Measurement issue	Detail on the challenge this issue presents	Impact on the direction of time reports from not addressing the issue as reported by the studies	Methods in reviewed studies to address the issues
Incremental care time	Whether to adjust total caregiving hours for those attributable to the health conditions of a recipient	Overestimation	Ask carers to explicitly report time due to the needs of the recipient’s health condition [40, 50] Ask carers to report care time before and after the onset of the recipient’s health condition [23] Between-subject comparison using regression adjustment and/or matching methods [43, 46, 47, 49, 53, 56] Difference-in-difference with propensity score matching [45]
	Whether to adjust reported caregiving for normal and caregiving-related time	No difference	Stratify carers between co- and extra-residential carers as evidence this is an issue [38] Comparison of reported household tasks with a time diary (between-subject comparison) [29]
Joint production	Whether to adjust hours for joint production	Overestimation	Adjust reported time from a time diary [58]
Time-bound tasks	Whether to obtain information on types of tasks
Time measurement method	Whether to collect direct observation, recall or time diary	Mixed (recall vs time diary)	Comparisons within individuals or across surveys between the recall method and the time diary method [28, 39, 41, 58, 60]
Intangible tasks	Whether to collect information on intangible tasks	Underestimation	Include intangible tasks in the questionnaire or time diary [22, 44, 59, 60]
	Whether to address large hourly reports	Overestimation	Subtract time from intangible tasks to allow the total caregiving hours not to exceed 168 h in a week [22, 44, 60]
Carer and recipient identification	Whether to collect information from the provider or recipient	Provider reported time greater than recipient reported time	Compare provider and recipient declarations of caregiving [55]
Multiple caregivers	Whether to collect information of further caregivers	Underestimation of total care time to a recipient	Obtain information from a non-primary caregiver [50, 51]
	Whether to use the primary or non-primary caregiver to collect information on all caregivers
Aggregation of informal care tasks	Whether to collect a global or task-based measure of caregiving time	Total time using one aggregated tasks question underestimated relative to separate tasks	Compare aggregated and separated tasks questions [58]
Non-response bias	Whether certain groups of carers are less likely to take part in surveys	Overestimation