Used for taxable fixed-income portfolios only, this figure takes into consideration all mortgage prepayments, puts, calls, and adjustable coupons. The number listed is a weighted average of all the maturities of the bonds in the portfolio, computed by weighing each maturity date (the date the security comes due) by the market value of the security. Since this is collected by survey, it is important to bear in mind that different fund companies may use different interest-rate assumptions in determining call likelihood and timing. Generally speaking, the longer the maturity, the greater the interest rate risk. When duration is unavailable, this is used in the calculation of the fixed-income style box.