Interesting article. Actually rather sophisticated considering it was written by an undergrad at Amherst.as his senior thesis. The article points out that the stock will likely initially move higher after being added to the S&P 500, followed over the longer term by a greater volatility in the stock's price swings. Those of us holding this stock over the past years are very experienced with the price volatility of biotech stocks, and the risks associated with investing in biotech in general. The nice thing about this point in time for Vertex is that it's prospects for tremendous growth and commercial success in it's pipeline has never been brighter, with multiple drugs in CF, autoimmune disease, influenza and hep C either in late or mid-stage clinical trials giving numerous opportunities for the company's commercial success approaching. Therefore, the market has good reason for why Vertex should be valued at $18 billion, specifically on the likely success of it's pipeline drugs starting with exponential growth expected in revenue and profits as Vertex gets it's CF franchise of drugs to market to treat the majority of patients with CF (with 'breakthrough drug therapy' status designated by the FDA) over the next 12 months. Increased volatility is good for traders but short positions are particularly at risk given the positive reaction likely from the market every time vertex announces positive results from the many clinical studies underway for it's drug candidates. The positions that will be taken by the S&P Index funds next Friday will reduce the number of shares available for trading, increasing the volatility of the stock, but also allowing more positive upward moves on good clinical trial results as well. Given the potential of the VRTX pipeline, it should be a very rewarding investment for investors over the next few years.