The resource inflow and outflow are based on estimates, using internal and external data combined with assumptions, and is then extrapolated to the total population based on sales volumes and inventory movements. Key assumptions are for resource inflow including actual weight of the materials found in two hearing aids and then multiplied with the total sales. In-house subject matter experts are consulted to reduce the risk of over- or understating. However, as the reported numbers are based on generic assumptions, numbers are subject to change when we gain access to more accurate data.