Why does a news item relating to one company often impact the share price of a company in the same sector?
On the face of it, if Tesco has a good set of results, that should be bad news for Sainsbury or Morrisons. In practice, the trading performance of companies is much more dependent on economic conditions than on how well they compete against their rivals, so a good set of results for one company is often a good omen for their sector peers. If you miss out on the rise (or fall) in the share price of a company after it issues a market moving trading statement, you can often still get involved in the action by trading the index (e.g. Food Retailers in the Tesco example).
