“…When time was valued by using a proxy, studies used either the wage of a paid carer [37,45,47,49,51) or the wage of a cleaner [40,41,52,56), irrespective of what informal care was undertaken. For studies that valued time by using the opportunity cost method, it was typically assumed that the carer had given up paid work to provide care and the studies variously used the average wage rate [29,30,37,43,47,57,54,55), minimum wage rate [36,39,45,46,50,51,53], actual wage of the carer [31,42], or wages of matched individuals [33] to value this time.…”