Ultrashort-bond portfolios invest primarily in investment-grade U.S. fixed-income issues and have durations typically of less than one year. This category can include corporate or government ultrashort bond portfolios, but it excludes international, convertible, multisector, and high-yield bond portfolios. Because of their focus on bonds with very short durations, these portfolios offer minimal interest-rate sensitivity and therefore low risk and total return potential. Morningstar calculates monthly breakpoints using the effective duration of the Morningstar Core Bond Index in determining duration assignment. Ultrashort is defined as 25% of the three-year average effective duration of the MCBI.