Commodity investments are typically made via futures contracts, as physical purchase of the commodity itself is not suitable for most investors. The returns on such commodity investments therefore depend not only on movements of the commodity spot price, but also on the income or loss from the rolling forward of expiring futures contracts. Roll returns are negative when the rolling forward of an expiring future into a longer dated future causes a negative cash flow due to their relative prices and positive when the reverse is true. The cumulative result of these cash flows over the course of a year is commonly referred to as roll yield which can be very significant to overall returns.