> Buying $100 of Company A and buying $10 of Company B shouldn't push up the price of Company A faster than Company B. Not necessarily. The price could change

> Buying $100 of Company A and buying $10 of Company B shouldn't push up the price of Company A faster than Company B. Not necessarily. The price could change in VERY different ways depending on the marginal supply and demand for each stock (i.e., how many more/fewer shares of the stock are other investors willing to buy/sell at different prices when the index fund goes out to buy that 0.0000001% of float). A tiny 'buyer-seller imbalance' in the stock market cause a big price adjustment.