1. Report Industry Investment Rating No information provided in the given content. 2. Core View of the Report - In the low - interest - rate era, "extending duration" and "controlling costs" are two key strategies for bond investment. The public - offering bond funds are shifting from "credit downgrading" to "duration management", and the low - cost advantage of bond - fund indexation is prominent [1][2]. - Long - duration index bond funds are the best combination of "high duration" and "low cost". Different types of long - duration index bond funds have different risk - return characteristics, and investors can choose according to their needs [3]. - Ten - year Treasury bond ETFs are effective "offensive - and - defensive" tools for enhancing portfolio returns, and are also suitable for short - term trading and rotation strategies [7]. 3. Summary According to the Directory 3.1 Low - Interest - Rate Era: "Extending Duration" and "Controlling Costs" as Two Key Strategies - Since early 2014, domestic interest rates have been in a downward cycle, and the upward elasticity of interest rates has weakened. From 2015 to 2025, the market has experienced five rounds of local government debt resolution, gradually flattening the credit spread [1][12][13]. - Facing the "low - interest - rate + low - spread" environment, public - offering bond funds are shifting from "credit downgrading" to "duration management". The average allocation ratio of medium - and long - term bond funds to credit bonds has dropped from 41% in 2020 to 30% at the end of Q1 2025, while the acceptance of portfolio duration is increasing [1][20][21]. - Referring to overseas experience, in a low - interest - rate environment, Japanese public - offering bond funds have increased their allocation to long - term bonds. In terms of risk - return ratio, the cost - effectiveness of long - duration strategies has become prominent since 2021 [27][32]. - Passive index - type bond funds have a cost - saving advantage of about 11 - 15bp per year compared with actively managed products, which is a relatively certain "hidden alpha" for investors [2][33]. 3.2 Long - Duration Index Bond Funds: The Best Combination of "High Duration" and "Low Cost" 3.2.1 Choices of Long - Duration Index Tools - Mainstream long - duration index bond funds are divided into three categories: local government bonds, Treasury bonds, and policy - financial bonds, and can be further divided into "long - term tools" (7 - 10 years and 10 years) and "ultra - long - term tools" (30 years) [3][48]. - Among them, the 10 - year index - type bond funds mainly hold bonds with a remaining term of 7 - 10 years, similar to 7 - 10 - year products. The 7 - 10 - year policy - financial bond index funds are the most popular, while the local bond index funds are scarce [48][49]. 3.2.2 Differences in the Long - Duration Index Toolbox - From the duration dimension, the 10 - year and 30 - year Treasury bonds have significant differences in risk - return characteristics, corresponding to the "ballast" and "offensive spear" roles respectively. The 10 - year Treasury bond is suitable for stable long - term investment, while the 30 - year Treasury bond is suitable for aggressive investors [54]. - From the bond type dimension, 7 - 10 - year policy - financial bonds are similar to Treasury bonds, while local bonds have unique characteristics. Although the long - term performance of 7 - 10 - year local bonds is good, investors may need more patience. The investment value of Treasury bonds and policy - financial bonds is converging [55][56][61]. 3.3 Investment Strategies for Long - Duration Index Bond Funds 3.3.1 Allocation: Enhancing Portfolio Returns, "Offensive and Defensive" - Ten - year Treasury bond ETFs are effective "offensive - and - defensive" tools for enhancing portfolio returns. In the interest - rate downward cycle, they have excellent return - capturing ability, such as the 9.02% annual return of Cathay Shanghai Stock Exchange 10 - Year Treasury Bond ETF in 2024 [7][65]. 3.3.2 Trading: Capturing Band - Trading Returns from "Point - Type Market Conditions" - Long - duration index products represented by ten - year Treasury bond ETFs have high liquidity and trading convenience, and are suitable for capturing band - trading returns from "point - type market conditions" in the bond market, such as the rapid decline and rebound of the 10 - year Treasury bond yield from November 2024 to January 2025 [7]. 3.3.3 Important Tools in Rotation Strategies - A "core - satellite" strategy is proposed, using long - duration interest - rate bond ETFs as the core "base" for pure - bond rotation, and tactically adjusting the satellite positions according to short - term market conditions. Back - testing shows that the improved rotation strategy can enhance returns and has better risk - adjusted returns [7][77][80].