Bond index funds can be a good idea for investors seeking exposure to a diversified portfolio of bonds. These funds aim to track the performance of a specific bond index, such as the Bloomberg Barclays U.S. Aggregate Bond Index or the FTSE World Government Bond Index. Bond index funds offer broad market exposure, diversification, and relatively low costs compared to actively managed bond funds. They can be suitable for investors looking for a passive investment approach and who want to achieve similar returns to the underlying bond index. However, it is essential to consider your investment objectives, risk tolerance, and time horizon before investing in any fund.