I understand that the F Fund is invested in Barclays U.S. Debt Index Fund, which tracks the Lehman Bros. US Aggregate Index. Since this is an index fund, it is not actively managed. Am I correct in assuming that given these facts, the bonds held are not adjusted with respect to maturities? For example, in times of rising rates, bonds with longer maturities are not replaced with shorter maturities. Thanks...:)