Other studies of listing and delisting of indices (like the S&P 500) show a similar result. The way that it has been explained in the past is that listing creates an increase in investor awareness, but that delisting doesn’t create a corresponding decrease in investor awareness. It likely means that investors are not yet very sophisticated in factoring in sustainability considerations. The initial listing creates some added investor awareness, but investors need a higher level of sophistication to track the delistings.