Negative At First But Positive Later

I have been doing quite a bit of thinking about how the Berkshire Hathaway addition to the S&P 500 will effect the market. I have come to the conclusion that the initial effect will likely be negative as other companies will be sold in order to buy Berkshire Hathaway. However, in the days following the index change the effect should be positive as holders of Burlington Northern and sellers of Berkshire Hathaway put some cash to work.