Beyond qualitative observations, the $($Q$,$ R$)$ system offers some quantitative insight into the factors that affect the optimal stocking policy. $($Example$)$ Increasing the average annual demand tends to increase or decrease the optimal order quantity Q$.$ For a given replenishment frequency, if customer service remains fixed $($at a sufficiently high level$),$ then the higher or lower the variability $($i$.$e$.,$ standard deviation of demand or replenishment lead time$),$ the more inventory we must carry.