Inclusions and Exclusions of Stocks in Cross-Border Investments: The Case of Stock Connect

How does the market react when more or fewer investors are allowed to trade certain stocks? Stock Connect, a cross-border investment channel between mainland China and Hong Kong, provides a natural testing ground. Investors are allowed to trade a list of qualified stocks from the stock market on the other side, and when a stock is removed from the list, investors can only sell but cannot buy that stock. We find that the inclusion of stocks is correlated with abnormal returns, implying downward-sloping demand curves for stocks. The effect weakens over time and disappears in about 40 trading days. There are no abnormal returns when stocks are removed from the list. On the other hand, when investors can only sell some stocks, they have a significantly higher propensity to sell. Their trading style becomes more contrarian for such stocks, and they tend to trade in small amounts. After 6 months, their investment behavior returns to that before the removal.