If they keep buying back shares there will come a tipping point. Usually triggered by them soaking up enough shares to get into the daily trading demand/turnover. I don't have a guess what that number is but it is out there somewhere.
Their retiring of shares will eventually constrict the number available for trading. It's a mathematical inevitability. But again, that number alludes me. It's going to be somewhere between the number of shares outstanding and the number held institutionally (a large portion of which would not trade as fluidly).
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