盘后票，即所谓的“after-hours trading”，是指在正式交易时间结束后仍然可以进行的证券交易。然而，盘后票常常被认为是假的，即存在一些问题和风险。下面将从市场深度、流动性和信息不对称三个方面来探讨盘后票为何存在这个问题。

首先，盘后票的市场深度相对较浅。在正式交易时间内，市场参与者众多，交易量大，市场深度较高，即买卖双方能够快速找到满足各自需求的交易对手。而在盘后交易中，由于市场参与者数量减少，交易量也相应缩小，导致市场深度不如正式交易时间。这就意味着，盘后票成交时可能会遇到买卖双方无法找到满意对手的情况，从而影响交易的效率和价格的形成。

Firstly, the market depth of after-hours trading is relatively shallow. During regular trading hours, there are many market participants and high trading volume, resulting in a deep market depth where buyers and sellers can quickly find suitable counterparties. However, in after-hours trading, the number of market participants decreases, leading to a smaller trading volume and a shallower market depth compared to regular trading hours. This means that during after-hours trading, there may be situations where buyers and sellers cannot find satisfactory counterparties, which can affect trading efficiency and price formation.

其次，盘后票的流动性也较低。在正式交易时间内，由于大量的交易参与者和活跃的交易量，市场的流动性较高，即证券能够被迅速买入或卖出，并且价格波动较小。然而，在盘后交易中，由于交易参与者减少，市场流动性降低，导致证券交易不太容易被执行，并且盘后票的价格波动较大。这样的情况给投资者带来了很大的不确定性，增加了盘后交易的风险。

Secondly, the liquidity of after-hours trading is lower. During regular trading hours, the market liquidity is high due to a large number of participants and active trading volume. This means that securities can be quickly bought or sold, and price fluctuations are relatively small. However, in after-hours trading, with fewer participants, market liquidity decreases, making it difficult to execute trades and resulting in larger price fluctuations. This situation brings significant uncertainty and increased risk to investors during after-hours trading.

最后，盘后票存在信息不对称的问题。在正式交易时间内，所有交易参与者都可以同时获取到同样的市场信息，从而在公平的基础上进行交易决策。然而，在盘后交易中，由于交易参与者数量减少，不同参与者之间的信息差异较大，存在信息不对称的情况。这样的情况可能会导致一些参与者拥有更多的信息和优势，从而影响到交易结果的公正性和均衡性。

Lastly, after-hours trading involves information asymmetry. During regular trading hours, all market participants can access the same market information simultaneously, enabling trading decisions to be made on a fair basis. However, in after-hours trading, with fewer participants, there is a greater disparity in information among different participants, leading to information asymmetry. This situation may give certain participants an advantage based on their possession of more information, which can affect the fairness and balance of trading outcomes.

综上所述，盘后票常常被认为是假的，主要是由于市场深度不足、流动性较低和信息不对称等问题。因此，投资者在进行盘后交易时应充分了解相关风险，并做好风险控制措施，以保护自身利益。

In conclusion, after-hours trading is often considered to be problematic due to insufficient market depth, lower liquidity, and information asymmetry. Therefore, investors engaging in after-hours trading should be fully aware of the associated risks and take proper risk management measures to protect their interests.