ハンセン指数リバランスと「フロントランニング」効果

The front-running effect is definitely a consideration, especially for less liquid stocks being added/removed. While large caps might absorb it, smaller constituents can see significant moves.

It's a valid question. While the market generally absorbs most of it, there are certainly institutional desks that specialize in anticipating these shifts. I've found it's less about the initial announcement and more about the gradual price discovery in the weeks leading up to the effective date.