超长债为何单独下跌，之后呢？

Group 1: Report Industry Investment Rating - No industry investment rating is provided in the report. Group 2: Core Viewpoints of the Report - The significant decline in ultra - long bonds is not expected to lead to a significant and continuous increase in the ultra - long bond spread in the long - term. However, short - term risks need further observation. As year - end bank indicator pressures ease, fund and brokerage positions decrease, and insurance allocation demand recovers, the ultra - long bond spread is expected to repair. But short - term risks, especially potential market shocks from concentrated selling by trading institutions, are hard to judge [5][21]. Group 3: Summary by Related Content Current Situation of Ultra - long Bonds - Recently, while other bonds remained stable, ultra - long bonds declined significantly. Since last Friday, medium - and short - term bonds were stable, with 2 - year and 5 - year Treasury yields fluctuating less than 1bp, and the 10 - year Treasury yield rising slightly by 1.1bp. In contrast, the 30 - year Treasury yield rose by 5.0bp, and the 50 - year Treasury yield rose by 5.9bp. This widened the spread between 30 - year and 10 - year bonds to 38.3bps, approaching the highs in late September and early October [1][8]. Reasons for the Weakening of Ultra - long Bonds - Banks' ability to hold long - term bonds is restricted by indicators such as △EVE and the Tier 1 capital ratio close to the 15% regulatory red line, which may lead to selling of long - term bonds to meet requirements or realize floating profits [2][10]. - The public fund fee reform may increase redemption pressure, and year - end net value drawdowns may exacerbate passive redemptions, causing trading institutions like funds and brokerages to reduce long - bond holdings [2][10]. - Insurance institutions' liability growth has slowed in the past two months, with a shift in allocation towards stocks. Insurance premium income growth was negative in September and October, and the proportion of bonds in asset allocation decreased slightly while the stock proportion increased [2][10]. Attractiveness of Ultra - long Bonds - From the perspective of the overall asset portfolio, the increase in ultra - long bond spreads enhances the cost - effectiveness of the barbell portfolio. With the same duration, the barbell portfolio's return is higher than that of the bullet portfolio, increasing the demand for ultra - long bonds and promoting a shift towards a barbell - shaped portfolio [3][12]. - In terms of absolute return, the increase in ultra - long bond yields makes them more attractive compared to other assets. The spread between the 30 - year Treasury and personal mortgage rates is at its lowest since Q3 2017, and considering tax, bad debts, and capital occupation, bonds are more cost - effective than loans. Ultra - long bond yields can cover the liability costs of insurance and banks, and with the slowdown in real - estate sales, future inflows of household deposits and insurance premiums are expected to increase, so the liability side is not a constraint for institutional allocation [4][14]. - Based on previous pricing of the 30 - 10 - year spread using factors like funding prices, net ultra - long bond financing, stock market performance, and ultra - long bond turnover, the current 30 - 10 - year spread is close to the upper limit of one standard deviation, indicating that ultra - long bonds are still within a reasonable range [4][17].