出手降温后，回答一下关于股市的四个问题

Core Viewpoint - The article discusses the recent regulatory changes in the Chinese stock market aimed at cooling down an overheated market, highlighting the adjustments in margin financing and the implications for investors [1][3][5]. Group 1: Regulatory Changes - The margin financing ratio has been raised from 80% to 100%, effectively reducing leverage from 1.25 times to 1 time for new financing contracts, while existing contracts remain unaffected [1]. - A significant sell-off was observed in major stocks, such as China Merchants Bank, with a sell order of 1.64 million shares, amounting to approximately 6.5 billion [1][2]. Group 2: Market Conditions - The stock market has been experiencing a surge in trading volume, nearing 4 trillion, with the top three highest single-day trading volumes in history occurring within the week [6]. - The net buying trend in margin financing has shown significant figures, with a total of 1.488 billion in the recent period compared to 1.412 billion earlier this year, indicating a frenzy among investors [8]. Group 3: Valuation Analysis - Despite the low interest rate environment, the stock market still presents relative value compared to other asset classes, as indicated by the historical comparison of the Shanghai Composite Index's price-to-earnings ratio and the 10-year government bond yield [12]. - However, certain sectors, such as the commercial aerospace sector, have seen exaggerated valuations, with companies like China Satellite exhibiting a static P/E ratio exceeding 4000 times, raising concerns about sustainability [16]. Group 4: Market Outlook - Historical data suggests that adjustments in margin financing ratios have not significantly impacted the short-term performance of the stock index [19][21]. - The dynamics of supply and demand will play a crucial role in determining stock price movements, with the balance between buying and selling pressure being a key factor [22][23]. Group 5: Recommendations - The article emphasizes the importance of regulatory improvements to ensure fair and transparent market operations, including better management of short selling and reducing the chaotic practices of fund platforms [26][28]. - Investors are advised to remain rational and seek structural opportunities within the market, as certain sectors may still offer promising investment potential despite overall market overheating [18].